Physics mcat
According to SOHCAHTOA, the initial vertical velocity is always _________ and the horizontal velocity remains constant at _____________. (projectile motion)
vsin(θ) vcos(θ)
imagine sending a __________, a single wavelength, down a string attached to a thread, a comparatively less dense medium, and observing its reflection.
wave pulse
frequency of a wave is determined by what
wave source
Work kinetic energy theorem Is express by which formula
W = delta K
Joules / Sec =
Watt
_____________ is light bending as it passes into a new medium
refraction
what is G equal to in newton's law of universal gravitation
6.67 X 10^11 (m^3)(kg^-1)(s^-2)
If the container pictured below is filled with an ideal fluid, which point in the fluid most likely has the greatest pressure? I___A_________I I I I I I B I____C____ I____________ I__________ ------------------D A. A B. B C. C D. D
B is correct The fluid at A and D are exposed to the atmosphere, so they must be at atmospheric pressure. The fluid at C is at the same level and velocity as the fluid exposed to the atmosphere and just leaving the pipe near point D, so the fluid at C must also be at atmospheric pressure. The fluid at B is at atmospheric pressure plus the weight of the fluid above it. The pressure at B is 1 atm + pgh
image distance will usually be represented as what two letters
Di or q
Hooke's law is given by the following equation
F = -k Δx
the formula for coulombs law is _______
F = k (q1)(q2) ________ r^2
in hydraulics, F1 / A1 is equal to what
F2 / A2
what is the formula representing newton's law of universal gravitation
F=G (m1m2) _________ (r^2)
two lenses put next to each other have a total magnification of their products and can best be represented by what formula
M = (m1)(m2)
____________ is an instrument that measures the current flowing through a circuit.
ammeter
then angle at which a wave reflects is called the _________
angle of reflection
__________ is the position of maximum displacement in a standing wave system.
antinode
a vector can be described be an _______
arrow
Δ E / t = t = time during which energy is transferred
P
what is the formula for Bernoulli's equation
P1 + (1/2)p(v1^2) + pgh1 = P2 + (1/2)(pv2^2) + pgh2
what is the formula for ideal gas law
PV = nRT
what is the SI unit of pressure?
Pascal (Pa)
________ states that pressure applied anywhere to an enclosed incompressible fluid will be distributed undiminished throughout the fluid.
Pascal's principle
W / T =
Power
(resistivity)(L) / A =
Resistance
the velocity of the fluid coming from the spigot in a tank can be derived from Bernoulli's equation as v =
Square root of (2gh)
Magnetic field strength is measured in units of ________
Tesla
a ___________ is a physical quantity that has magnitude but no direction
scalar
__________ occur only when different frequencies of light pass through a lens simultaneously.
chromatic aberrations
As a result, white light, which is made up of all light frequencies in the visible spectrum, is split by a prism in the phenomenon known as ____________
chromatic dispersion
light is said to be ______________ when it consists of electric fields of constant magnitude that change direction in a rotary manner
circularly polarized
_________ system allows exchange of energy with the surroundings but not exchange of mass.
closed system
__________ is typically created by placing a single slit screen in front of the double slit screen and using a monochromatic light source
coherence
in capillary action, the intermolecular forces responsible for surface tension are called what
cohesive forces
a diverging lens is a _________ lens, meaning that its center is thin relative to its periphery
concave lens
good ________, allow electrons to flow relatively freely.
conductors
in thin film interference, __________ results when the thickness of the film is equal to a multiple of half the wavelength of light within the medium of the thin film.
destructive interference
the _________________ refers to the substance between the plates of a capacitor.
dielectric constant, k
At some maximum voltage, the dielectric will break down and conduct electricity. This value of a dielectric is called the ___________
dieletric strength
________ is the spreading of light that occurs when a wave bends around the edges of an object or opening
diffraction
the power of a lens is measured in _________
diopters
___________occurs at the fluid-object interface and is a force working against flow
drag
if any velocities are nonzero but all velocities are constant, the system is in _________________ equilibrium
dynamic
what is the charge of one electron unit
e = 1.6 x 10^-19 C
___________ means no net force and no net torque, therefore no acceleration
equilibrium
see standing fluids, think forces in ________
equilibrium
___________ properties change with the quantity of a substance
extensive
properties that are concerned with quantity, like mass and energy are called _________
extensive properties
A _____________ is some type of distortion or condition in space that creates a force on a charge
field
the __________ is the pressure experienced by the object as a result of the impulse of molecular collisions.
fluid pressure
only ______ and __________ forces act at a distance
gravitational electromagnetic
___________ is the attractive force that every mass in the universe exerts on every other mass in the universe.
gravitational force
______ is a simple machine that works via Pascal's principle. Two pistons and a container enclose a standing incompressible fluid.
hydraulic lift
how do ideal fluids differ from real fluids? (4 ways)
ideal fluids have no viscosity ideal fluids are incompressible ideal fluids lack turbulence ideal fluids experience irrotational flow
_______ machine reduces the force required without changing the work required
ideal machine
the focal point of a concave mirror lies where
in front of the mirror
density and pressure are examples of what property type
intensive
Surface tension is also responsible for the formation of water droplets. The ____________________ pull inward, minimizing the surface area by creating a more spherical shape.
intermolecular forces
real images are always upright or inverted?
inverted
_____________ system allows no exchange of energy or mass with the surroundings
isolated
When the relative velocity brings the source and observer closer, what happens to observed frequency?
it goes up
the unit of energy used on the mcat is the __________
joule
what are the SI units of density?
kg / m^3
a specific gravity of _____________ than one indicates a substance lighter than water
less than one
a ____________ is a beam attached to a fulcrum (pivot point)
lever
_________ is the transfer of energy through alternating electric and magnetic fields
light
an artificial scale for intensity level has been created based upon a ____________ of intensities
logarithmic scale
a __________ such as a sound wave, is one in which the medium is displaced parallel to the direction of wave propagation
longitudinal wave
The path of a projectile that is not experiencing air resistance is not influenced by the ___________ of the projectile.
mass
__________ is the quantitative measure of an object's inertia
mass
when an object is floating, ____ are equal
masses
_____________ is the energy of a macroscopic system
mechanical energy
according to the rules of SOH CAH TOA, the normal force is always equal to ___________
mg cosθ
whenever you see an inclined plane, think ___________
mg sin θ
when a wave reflects off a medium that is __________ dense, it is inverted
more
in convergers, when an object is placed within the focal length, the image will be ___ and ________
virtual and upright
the ___________ is the density of that substance compared to the density of water.
specific gravity
a _________ is produced by the apparent convergence of light rays; there are no light rays actually present at the location of the perceived virtual image.
virtual image
a __________is an instrument that measures the potential difference between any two points on a circuit.
voltmeter
newtons ____________________ states that an object in a state of rest or in a state of motion will tend to remain in that state unless it is acted upon by a net force.
newtons first law of motion, the law of inertia.
Distance _________ = Time
speed
one joule is 1 kg m^2/s^2 which is the same as ________ N m
1
__________ is the volume of fluid which passes per unit time.
volume flow rate. represented by Q
in convergers, if p is = to f the image is located where? the image has a positive or negative q? the image is virtual or real? the image is upright or inverted?
no image formed
______ is a system in which some of the energy transferred as work done on the machine is lost to friction, deformation, and/or other inefficiencies
non-ideal machine
all angles in snell's law are measured from the _________, an imaginary line that is perpendicular to the surfaces that interface.
normal
the force of the inclined plane pushing back against the block is called the ___________
normal force
the two converging lenses used in a microscope or telescope are called the _________ and the _________
objective eyepiece
how would you calculate capacitors in series?
(1/Ctotal) = (1/C1) + (1/C2) + (1/C3) ..
thin film interference is the result of what 3 things
1. phase changes associated with reflections off media that are more dense 2. path length differences 3. wavelength changes associated with changes in media
what is the index of refraction for water
1.3
An increase in which of the following lens properties will increase the power of a lens? I. index of refraction II. focal length III. radius of curvature on one side of the lens A. I only B. I and II only C. II and III only D. I, II and III
A. I only An increase in the index of refraction of a lens would increase the bending of the light rays, which would increase the power of the lens. Therefore, I would increase the power of the lens; choice C can be eliminated. Since p= 1/f, an increase in f would decrease the power. Therefore, II would not increase the power of the lens; choices B and D can be eliminated. Choice A, I only, is the correct answer choice. To confirm, consider whether III would increase the power of the lens. Increasing the radius of curvature of one side of the lens would flatten the lens, reduce the degree to which it bent light and decrease its power. Thus III would not increase the power of the lens and A is the best answer
All of the following are examples of wave diffraction EXCEPT: A. a light wave bends when passing from air to water B. music is audible around a corner from the source C. the shadow cast by statue is blurred at the edges D. ripples in water become semicircular after passing through a small space.
A. a light wave bends when passing from air to water. A light wave bending as it enters a new medium is refraction, not diffraction. Diffraction occurs when waves bend around corners. Although the other answer choices may have been difficult to identify as diffraction, you should have been able to identify that choice A was an example of refraction.
Current is given in _________
Amps (A), C/s
______________ states that the sum of the pressure, kinetic energy per unit volume, and potential energy per unit volume of a fluid remain constant throughout the fluid.
Bernoulli's equation
_______________ restates conservation of energy in terms of densities and pressures, the intensive properties used to describe fluids.
Bernoulli's equation
When the frequency of a sound wave is increased, which of the following will decrease? I. wavelength II. period III. amplitude A. I only B. III only C. I and II only D. I and III only
C. I and II Frequency is inversely related to both wavelength and period; options I and II are true. There is no relationship between amplitude and frequency; option III is false. Therefore choice C is the best answer
The diagram below shows an object placed in front of an unknown optical device and the image produced. __________ ^ object I I I I I I I I ----------------------------------------------------------------------- I I I I _________ I I image V The optical device is a A. convex mirror B. concave mirror C. converging lens D. diverging lens
C. converging lens According to the figure, the optical device forms an inverted image on the opposite side of the device from the object. Only converging mirrors and lenses form inverted images. Therefore, choice A, convex (diverging) mirror, and choice D, diverging lens can be eliminated. Remember that inverted images are always real images. Therefore, the image formed must be a real iamge. Real iamges formed by mirrors are on the same side of the mirror as the object, whereas real images formed by lenses are on the opposite side of the lens from the object. Recall that a real image is formed by an actual convergence of light rays. Mirrors reflect light back towards objects whereas lenses refract light as they pass through to the opposite side of htel ens from the object. Because the real image is on the opposite side of the optical device from the object, the optical device must be a lens. Therefore, choice B, concave (converging) mirror can be eliminated and choice C, converging lens, is the best answer.
The diagram below shows a cross-sectional view of a cylindrical pipe of varying diameter. If an ideal fluid is flowing through the pipe, all of the following statements are true EXCEPT: ___________________ ___________/ --------------> \_________________________ ___________ A _______________B__________ \__________________/ A. the cross-sectional area is greater at point A than at point B B. the pressure is lower at point B than at point A C. the volume flow rate is greater at point A than at point B D. the flow speed is greater at point B than at point A.
C. the volume flow rate is greater at point A than at point B. For ideal flow, volume flow rate Is constant at all points, so the volume flow rate will be equal at points A and B. Answer choice A is a correct statement as seen in the diagram. Since the flow rate stays constant, decreasing the cross sectional area, A, will increase the velocity of the fluid, Q = Av. Increasing the velocity will increase the 1/2 pv^2 term in Bernoulli's equation. thus the pressure term, P, must decrease. The pressure will be lower where the fluid is moving faster, in this case at point B.
how would you calculate capacitors in parallel?
Ctotal = C1 + C2 + C3
what are the two formulas to express density of water
D = 1000 kg / m^3 = 1 g / cm^3
Mercury has a specific gravity of 13.6. The column of mercury in the barometer below has a height h = 76 cm. If a similar barometer were made with water, what would be the approximate height of the column of water? A. 5.6 cm B. 75 cm C. 154 cm D. 1034 cm
D. 1034 cm Atmospheric pressure supports the column of fluid. The pressure at the bottom of the column must be equal to atmospheric pressure. The pressure is equal to pgh. If p is decreased by a factor of 13.6, the height must be increased by the same factor. Notice that, given the choices, there is no need to do the math. Each other answer is less than 10 times as tall. Answer choice B can be eliminated immediately because the height of the column depends on the density of the fluid. changing density must therefore change the height. Likewise, answer choice A is incorrect because a less dense fluid will be pushed up the barometer higher than a more dense fluid
An ideal fluid with pressure P flows through a horizontal pipe with radius r. If the radius of the pipe is increased by a factor of 2, which of the following most likely gives the new pressure? A. P B. 4P C. 16P D. the new pressure cannot be determined without more information
D. The new pressure cannot be determined without more information The cross sectional area A is increased by a factor of 4 when r is doubled. A = pi r^2. since q remains constant, the velocity decreases by a factor of 4, Q = Av. From Bernoulli's equation, we see K = P + 1/2 pv^2. When the velocity decreases by a factor of 4, the 1/2 pv^2 term decreases by a factor of 16; however, the actual amount is unknown, thus the amount that P increases cannot be calculated ( P and 1/2pv^2 are added, not multiplied, therefore the absolute values must be known.
The resting voltage across the membrane of a neuron is measured at -70 mV. In multiple sclerosis, the axons of neurons lose their myelin sheath. This results in 30% decrease in the resistance of the membrane. What is the current flow across one cm of an axon in a patient with multiple sclerosis? Assume that the resistance of a healthy axon is 250 MΩ/ cm. A. 2 x 10^-10 μA B. 4 x 10^-10 μA C. 2 x 10^-4 μA D. 4 x 10^-4 μA
D. is correct Use Ohm's Law, i = V/R. The resistance of one cm of membrane in a neuron with multiple sclerosis is 0.7 x (250 MΩ) = 175 MΩ. Don't forget to convert to SI units. i = V/R = (7 x 10^-2 V) / (1.75 x 10^8 Ω) = 4 x 10^-10 A = 4 x 10^-4 μA
V / R =
I (electric current)
how do you calculate mass flow rate, I?
I = pQ = pAv
energy consumption in the home is generally measured in units of kilowatt hours. A kilowatt hour is equal to: A. 3600 J B. 6000 J C. 3,600,000 J D. 6,000,000 J
Kilowatts are a unit of power, which is a measure of energy transfer per unit time. 1 W = 1 J/s. Therefore, 1 kW = 10^3 J/s and 1 kilowatt hour = (10^3 J/s)(60 s/min)(60 min/hour) = 3600 x 10^3 J = 3,600,000 J. C is the best answer.
________________ states that when only conservative forces are acting, the sum of mechanical energies remains constant.
Law of conservation of mechanical energy
what is the continuity equation and its components?
Q = Av v = velocity A = cross-sectional area
how would you calculate resistors in series
R(total) = R1 + R2 + R3 + ...
each point along the mirrors surface is equidistant from the center of curvature. This distance between the surface of the mirror and its center of curvature is known as the ____________
radius of curvature
________________ motion that contributes to fluid pressure as in a fluid at rest
random translational motion
what are the two types of motion of molecules of a moving fluid
random translational motion uniform translational motion
A car accelerates at a constant rate from 0 to 25 m/s over a distance of 25 m. Approximately how long does it take the car to reach the velocity of 25 m/s? A. 1 s B. 2 s C. 4 s D. 8 s
This problem may be tricky because the question only implies a necessary variable. That variable is initial velocity. The initial velocity is zero. The average velocity of any constantly accelerating object that starts with zero velocity is the final velocity divided by 2. This is from v avg = (v + v0) / 2. In our case, v avg = (25ms/ + 0 m/s)/2 = 12.5 m/s. Then the average velocity times time equals displacement, (vavg)(t) = x. Here, (25m)/(12.5m/s) = 2s.
(1/2) (Q^2)/(C) =
U
1/2 C(V^2) =
U
1/2 QV =
U
The potential energy of a charge is calculated using which formula
U = qEd d= measured from a zero point of our own choosing, similar to variable h in gravitational potential energy
A deformed object following Hooke's law has an elastic potential energy given by the formula :
U(elastic) = 1/2 k (delta x ^2)
mgh =
U(gravity)
gravitational potential energy is given by what formula?
U(gravity) = - (G(m1)(m2)) ___________ r
formula for gravitational potential energy of an object near earth's surface
U(gravity) = mgh
_____________ , light is projected onto a screen with two small slits. The light is monochromatic and coherent. The light waves diffracting through the two slits interfere with one another and produce a predictable pattern of alternating light and dark bands
Young's double slit experiment
a ____________ acts to resist the creation of an electric field, allowing the capacitor to store more charge.
a dielectric
a __________ is a horizontal tube with a constricted region -- a region with decreased cross-sectional area - in its middle.
a venture tube
_______ is the propagation of that vibration from one point to another.
a wave
gauge pressure + atmospheric pressure =
absolute pressure
pressure measured relative to a vacuum is called __________
absolute pressure
an object travelling at 10 m/s north one moment and 10 m/s east the next moment has __________, even though its speed has not changed.
accelerated
any change in velocity is _________, whether it is a change in magnitude, direction, or both
acceleration
change in velocity __________________ = time
acceleration
on a velocity versus time graph, the slope is _________
acceleration
the rate of change in velocity is a vector quantity called _____________
acceleration
in capillary action, the forces between the molecules of the tube and fluid molecules Is known as ________
adhesive forces
As mentioned above, resonance is impacted by the fact that real waves under go ____________: the decrease in the intensity of a wave propagating through a medium.
attenuation
when __________ forces are acting, the total mechanical energy, meaning the sum of potential and kinetic energies, remains constant.
conservative forces
when the diffracted waves meet in young's double slit experiment, interference forms bright and dark __________
bands
A __________ adds energy to a circuit
battery
_________ occur when two waves with slightly different frequencies are super-imposed.
beats
focal point of a convex mirror is located where
behind the mirror, where rays appear to converge
Problems about fluids at rest can be thought of as problems about forces. A standing fluid exerts a force called the ___________________ on any object that is floating, submerged, or sunk in the fluid
buoyant force
a ________________ is used to temporarily store energy in a circuit
capacitor
______________ is a phenomenon related to surface tension in which fluid is pulled up a thin tube.
capillary action
the buoyancy force acts on an object's ___________
center of buoyancy
___________ is a point from which the charge generated by an object or system of objects can be considered to originate
center of charge
each point along the mirrors surface is equidistant from the _________
center of curvature
at the center of the imaginary sphere would be a point called the ____________
center of curvature.
___________________ is the single point at which all of the system's mass can be considered to be concentrated.
center of mass
_____________ occurs when the sum of the displacements results in a greater displacement.
constructive interference
in thin film interference ________ occurs when the thickness of the thin film is equal to a multiple of one quarter of the wavelength of light within the thin film
constructive interference
in young's double-slit experiment, waves interfere ________ when the difference in path length, is a multiple of λ, and __________ when path length is a multiple of λ/2
constructively destructively
______ are capable of forming both real and virtual images
convergers
___________ usually form images that are inverted, real, and located on the side of the observer
convergers
when the object is located beyond the focal point, _________ will always produce a real, inverted image, located on the side of the observer
convergers
the units of the logarithmic scale to measure intensity level of sound is known as
decibels (dB)
an object is said to have _____________ energy, when a restorative elastic force acts on it.
elastic potential energy
____________ is defined as the electrostatic force per unit charge
electric field
____________ do not require a medium through to travel
electromagnetic waves
The ratio of speed of light in a vacuum, c, to the speed of light in a particular medium, v, is known as the medium's __________
index of refraction
Whether they are moving or at rest, all objects have a tendency to remain in their present state of motion. This tendency is called _________
inertia
on the longer wavelength just beyond the visible spectrum is ___________
infrared
when the speed of an object is constantly changing, the ____________ is the speed of an object at a particular moment (instant) in time
instantaneous speed
10 log (I / I(sub zero)) =
intensity level (B)
resistance is measured in __________
ohms
The smallest possible unit of charge is ________
one electron unit
how many focal points does a mirror with a single curve have
one focal point
when the thickness of the film in in thin film interference is equal to half the wavelength, the wave will travel _________ wavelength
one full
___________ system allows exchange of energy and mass with the surroundings
open system
what are the 3 basic types of systems in the universe?
open system closed system isolated system
virtual images are located on which side of the lens or mirror
opposite
multiple lens systems will likely appear in the context of ____________, which manipulate the properties of light to produce viewable images
optical instruments
in a ________________ two plates made from conductive material are separated by a very small distance. On a charged capacitor, one plate holds positive charge, and the other plate holds the exact same amount of negative charge
parallel plate capacitor
_______ is the number of seconds required for one wavelength to pass a fixed point
period
_____________ is the number of seconds required for one wavelength to pass a fixed point.
period
Just as frequency does not change when a wave moves from one medium to another, neither does the ________
period (T)
contact forces must act in at least one of which two directinos
perpendicular to a surface and/or parallel to a surface
within an electric field, movement perpendicular to the field does not result in a change of _________
potential
a mechanical energy can be further divided into ______ and ________ energy
potential and kinetic
___________ is the energy of position
potential energy
The _______ of a lens is the inverse of the focal length
power
the amount of work done by a force per unit time is described in terms of ____________
power
the lens strength of a lens, also called ________, is determined by its focal length
power
1 / (focal length) =
power of a lens
force over area =
pressure
most common light sources emit light that is ___________ polarized; the electrons emitting the light have no preferred vibrational direction
randomly polarized
the ______________ occurs via the vibration of a source such as the vocal cords
production of sound
the movement of an object through the air along a curved path due to gravity, is called _______
projectile motion
_____________ allows force to act over a greater distance so that the same amount of work can be done with less force.
pulley
a ____________ is a conical wave front, produced when the velocity of the sound source exceeds the velocity of the sound wave
shock wave
in convergers, if p is greater than f, the image is located where? the image has a positive or negative q? the image is virtual or real? the image is upright or inverted?
side of the eye positive q real inverted
___________ for work provide a standardized way to show where energy is coming from and where it is going.
sign conventions
how do you calculate the critical angle
sin^-1 (n2 / n1)
the greater the index of refraction for a medium, the more ____________ light moves through that medium
slowly
_________ is the transfer of energy through oscillations between high and low pressure.
sound
Imagine two endless rows of since waves travelling in opposite directions on the same string. the string would hold perfectly still at the nodes and move violently up and down at the antinodes. This condition is known as a __________.
standing wave.
if all velocities are zero, the system is in ___________ equilibrium
static
_______ flow means that all fluid flowing through any fixed point has the same velocity.
steady flow
the concept of _______________ was created to allow visualization of an ideal fluid. a ______ is a path followed by a hypothetical fluid particle.
streamlines streamlines
what are the two forces existing within the nucleus of an atom
strong nuclear force weak nuclear force
While two magnifications of lenses are multiplied by each other, they have an effective product power equal to the __________ of their individual powers
sum P(total) = P1 + P2
_____________ describes the intensity of the intermolecular forces of a fluid per unit length
surface tension
a ___________ is any defined area that we choose to consider separately from the rest of the universe
system
what does newtons second law state
that when a net force acts on an object, the change in that object's state of motion will be inversely proportional to the mass (m) of the object and directly proportional to the net force (F) acting on the object.
what is newton's first law of motion called
the law of inertia
__________ is the time it takes the wave to travel the distance of one wave-length and is the reciprocal of frequency
the period
a specific gravity of _____________ than one indicates a substance is equally as heavy as water
the same as
a system is any defined area that we choose to consider separately from the rest of the universe. The rest of the universe is called ________________
the surroundings
___________ is a measure of a force's ability to cause rotational acceleration
torque
When light is coming from a medium with a higher index of refraction, the angle of incidence can be so great as to cause ____________. In other words, if the angle of incidence is large enough, all photons will be reflected at the angle of reflection, and non will refract. This angle is called the ________
total internal reflection critical angle
__________________ in contrast, is produced by forces acting at an objects center of mass.
translational motion
the peak height of a projectile can be found by using which equation
v = Square root (2gh)
wave velocity is commonly express as which formula
v = fλ
a ___________ is a physical quantity with both magnitude and direction
vector
changing the magnitude or direction of a vector creates a new _________
vector
_________ is the slope of a displacement vs. time graph
velocity
__________is the distance a wave travels per unit time
velocity
a venture tube can be used to determine the _________ of a fluid that is flowing within it
velocity
displacement ______________ = time
velocity
on a displacement versus time graph, the slope is _____________
velocity
static and dynamic equilibrium are both defined by constant __________
velocity
the _________ of a wave describes the distance over which the wave travels per unit time, and is determined by the medium through which the wave travels.
velocity
the decrease in pressure that occurs when a fluid flows into a constricted region of a pipe is known as the ____________
venture effect
a ____________ can be used to determine the velocity of a fluid in a pipe
venturi meter
ramps do not change the amount of _________ done
work
___________ is energy transferred for any reason other than a temperature difference
work (w)
in _______________, x-rays are projected at a crystal scatter and create regular interference patterns unique to the structure of the crystal.
x-ray diffraction
a battery's energy is calculated using which formula
ΔG = -nFE
In a horizontal pipe of constant cross-sectional area, fluid will flow from high pressure to low pressure according to what equation? (non-ideal fluids)
ΔP = QR
how would you calculate resistors in parallel
(1/Rtotal) = (1/R1) + (1/R2) + (1/R3) etc
what is the thin lens equation?
(1/f) = (1/do) + (1/di) do = object distance di = image distance
atmospheric pressure is equal to how many pascals
101,000 Pa
unlike a mirror, a lens has how many focal points?
2, because it has two curved surfaces
a 50 kg skydiver and a 100 kg skydiver open their parachutes and reach a constant velocity. The net force on the larger skydiver is: A. equal to the net force on the smaller skydiver B. twice as great as the net force on the smaller skydiver C. four times as great as the net force on the smaller skydiver D. half as great as the net force on the smaller skydiver
A. equal to the net force on the smaller skydiver. Since both skydivers are at constant velocity, their acceleration is zero, and by newton's second law they must both experience a net force of zero.
Which of the following changes to a parallel plate capacitor would not increase its capacitance? A. Decreasing the distance between the plates B. increasing the area of the plates C. Increasing the dielectric constant D. increasing the voltage across the plates
D. increasing the voltage across its plates. Increasing the voltage across the plates would increase the amount of charge on the capacitor but not the capacitance of the capacitor. Capacitance is defined by C = Q/V. All the other choices, distances between the plates, area of the plates, and the dielectric constant change the capacitance.
All of the following are indicative of the wave nature and not the particle nature of light EXCEPT: A. diffraction B. interference C. dispersion D. reflection
D. reflection. The observation that light is reflected could fit either the wave or particle of light. However, the other choices all provide support for the wave theory of light. Therefore D is the best answer.
1/2m(v^2) =
K
what is the formula for kinetic energy
K = 1/2 (m)(v^2)
_______________ states that for every action, there exists an equal and opposite reaction.
Newton's third law
weight is measured in _________
Newtons (N)
A driver moving at a constant speed of 20 m/s sees an accident up ahead and hits the brakes. If the car decelerates at a constant rate of -5 m/s^2, how far does the car go before it comes to a stop? A. 10 m B. 20 m C. 40 m D. 100 m
The deceleration is 5 m/2^2, so the velocity is reduced by 5 m/s each second. After 1 second the velocity is 15 m/s; after 2 seconds, 10 m/s, after 3 seconds, 5 m/s, and after 4 seconds, 0m/s. so the car stops in 4 seconds. The average velocity for motion with constant acceleration is the midpoint between the starting and ending velocities. The midpoint between 20 m/s and 0 m/s is 10 m/s. The average velocity times the time is 10 m/s x 4s = 40 m
All of the following describe the magnitude and direction of a vector except: A. 10 m/s west B. 10 m/s in a circle C. 20 m to the left D. 20 m straight up
The direction for a vector must specify a straight path. A straight arrow cannot be drawn to represent a circle; choice B is not a vector A. is a velocity vector C and D are displacement vectors
A box starts from rest and slides 40 m down to a frictionless inclined plane. The total vertical displacement of the box is 20 m. How long does it take for the block to reach the end of the plane? A. 1 s B. 2 s C. 4 s D. 8 s
The force parallel to the unit is mg sinθ. Use newton's second law to calculate the acceleration down the incline. F=ma mgsinθ = ma --> a = g sinθ The sine of θ Is opposite over hypotenuse which is 20/40 = 1/2. Thus the acceleration is 1/2 g or 5 m/s^2. Substitute this into linear motion equation and solve for time: x=(v0)(t) + 1/2(a)(t^2) 40 m = (0m/s)t + 1/2(5 m/s^2)(t^2) 16 s^2 = t^2 and t = 4 s
a ____________ refracts light rays such that they converge at a point on the side of the lens opposite the light source
converging lens
a ____________ reflects light rays such that they converge at a point in front of the mirror
converging mirror
If the electric field is created by a point charge, we can derive the electric potential energy using ________
coulomb's law U = K (q1)(q2) _________ r
charge (q) is given in units of ___________
coulombs
the ____________ is derived from Snell's law by recognizing that the angle of refraction is 90degrees and that sin90 = 1
critical angle
the atoms of ________ are roughly the correct distance apart to act as a natural diffraction grating for x-rays
crystals
moving charge is called ___________
current
interference patterns can also be observed when light is passed through more than two slits. A ______________ is a series of many small slits that diffracts a light source into its component colors. The slits are called rulings
diffraction grating
velocity and acceleration do NOT have to be in the same _________
direction
_________, a type of refraction, is the splitting of light according to frequency
dispersion
____________ is the separation of light into different frequencies due to their different indices of refraction in a medium.
dispersion
____________ refracts light rays such that they appear to converge at a point on the same side of the lens as the light source, opposite from the side of the observer.
diverging lens
__________ lenses and mirrors always form virtual, upright images located on the opposite side from the observer
diverging lenses
a ___________ reflects light rays such that the observer perceives them as converging at a point on the opposite side of the mirror from the observer
diverging mirror
batteries are rated by _______________, which is a fancy word for voltage
electromotive force (EMF)
_________ is a state in which there is no net force and no net torque.
equilibrium
When the electron loses energy, it falls into one of those intermediate states, emitting ___________ with wavelengths in the visible light range
fluorescent
the ________ of a lens is affected by the refractive index of the lens and the substance surrounding the lens
focal length
the ______________ is equal to half the radius of curvature
focal length
the distance between a mirror and its focal point is known as the _______
focal length
R/2 (in regards to mirrors) =
focal length (R = radius of curvature)
every mirror or lens has a characteristic _________ at which parallel light rays converge or appear to converge after reflecting off of the mirror or passing through the lens
focal point
___________ is the number of wavelengths that pass a fixed point in one second
frequency
the ______________ of a wave is the number of wavelengths that pass a fixed point in one second.
frequency (f)
_________ is a force that opposes relative motion. It is caused by attractive molecular forces between surfaces that are in contact.
friction
____________ is the potential energy created by the force of gravity.
gravitational potential energy
a specific gravity of _____________ than one indicates a substance is heavier than water
greater than
___________ is energy that is transferred between a system and its surroundings due to a temperature difference between them
heat (q)
what are the two types of energy transfer?
heat and work
When closely packed atoms, such as those in a solid, are subjected to high temperatures, their electrons transition not only between energy levels within a single atom, but also between atoms. Because their electrons can make an infinite number of transitions, they produce ___________
incandescent light
________ is the velocity of an object in motion at a specific point in time.
instantaneous velocity
_______ a measure of loudness, describes how intense a sound seems to be.
intensity level
_____________ properties are concerned with the intrinsic nature of a substance and thus do not change with the quantity of a substance.
intrinsic
because the product of force and displacement is equal to a constant, these variable are said to be _________________ to each other
inversely proportional
_________ means any object moving with an ideal fluid will not rotate about its axis as it flows, but will continue to point in one direction regardless of the direction of flow.
irrotational flow
on the mcat, mass is usually measured in _______
kilograms
__________ is the energy of motion.
kinetic energy (K)
K1 + U1 = K2 + U2 confirms which law
law of conservation of mechanical energy
In reality, images are often blurred and exhibit departures from theoretical images called _______
lens aberrations
the __________ also called power, is determined by its focal length
lens strength
thicker center converges means what
lenses with thicker centers converge (i.e. convex lenses)
when a wave reflects off a medium that is _________ dense, it is reflected upright
less
what is the magnification formula?
m = - (di / do) = Hi / Ho distance image / object distance = image height / object height
what are the units of diopters
m^-1
___________ reduce the force required to do a given amount of work
machines
the ability to reduce applied force is referred to as ______________
mechanical advantage
some waves, called _____________, obey the laws of classical mechanics and require a medium, or substance, through which to travel
mechanical waves
velocity of a wave is determined by what
medium
wavelength is determined by what
medium
the net force due to gravity and the normal force of an inclined plane is always equal to __________ and points in a direction that is parallel to the plane
mg sinθ
c / v =
n index of refraction
an image on the opposite side from the observer is defined as ___________
negative
_________ is the sum of all net forces acting on an object.
net force
____________ states that when a net force acts on an object, the change in that object's state of motion will be inversely proportional to the mass of the object and directly proportional to the net force (F) acting on the object
newton's second law
does refraction change the phase of the wave at the interface between two media
no
the pushing and pulling forces applied by animals are ___________.
non-conservative
the perpendicular force to a surface is all called the ______
normal force
in convergers, if p is less than f, the image is located where? the image has a positive or negative q? the image is virtual or real? the image is upright or inverted?
opposite side from the eye native q virtual upright
as the vocal cords vibrate, they create sound waves that travel from point to point as _____________, or regular variations, between high and low pressure.
oscillations
Whether interference is constructive or destructive depends on the ________ of the wave, which relates to its wavelength, frequency, and place and time of origin
phase
The light emitted by electrons is in the form of ________, pulses of electromagnetic radiation that can be thought of a localized particles of energy
photons
_______________, is a measure of how "high" or "low" a note sounds, correlates with frequency; a high note has high pitch and high frequency.
pitch
The angle of incidence is equal to the angle of reflection when light reflects off a ____________
plane (flat) surface
When light is ______________, its electric and magnetic fields are oriented in a particular, rather than a random way.
polarized
________ is the distance from the point of rotation to the point of application of the force.
position vector
an image on the same side as the observer is, by convention, defined as ________
positive
a flatter spherical mirror has a larger _________
radius of curvature
________ is an inclined plane that reduces the force needed to do work by increasing the distance over which the force is applied.
ramp
depending on the type of mirror lens, the image that is produced can be ________, meaning that light rays actually meet at a physical point, or _________, meaning that the brain of the observer fills in an image at the point where the light rays would converge if they were traced back to an imaginary origin.
real virtual
a ________ is a point at which light rays actually converge, whereas a ________ is a point at which light only appears to converge.
real focal point virtual focal point
a __________ is derived from the actual convergence of light rays.
real image
In convergers, when an object is located beyond focal point, a _____, _________ image located where will be produced?
real, inverted image located on side of the observer
the order of the 3 primary colors of light from low frequency to high frequency is what
red, then green, then blue
____________ is light bouncing off the boundary between media
reflection
when a wave reaches an interface between two media, it can be altered through either ____________ or _____________
reflection refraction
in thin film interference, at each surface, light can reflect or refract. If it _______, it changes wavelength but not phase. If it __________, it changes phase but not wavelength. and if it ________ off a medium that is less dense, it changes neither wavelength nor phase
refracts reflects reflects
The quantitative measure of an object of a particular shape and size to resist the flow of charge is called its ____________
resistance
As we learned earlier, all substances resist the flow of charge. The quantitative measure of this property is called _________
resistivity (p)
good __________, hold electrons tightly in place.
resistors
The condition where the natural frequency and the driving frequency are equal is also called ________
resonance
standing waves cause the string to _____________ or vibrate at its natural frequency or resonant frequency
resonate
___________ is produced by forces acting at points other than an objects center of mass.
rotational motion
real images are located on which side of the lens or mirror
same side
____________ arise when rays farther from the center of a lens focus at different points than do rays closer to the center of the lens.
spherical aberrations
_______ are mirrors in the shape of a portion of a sphere
spherical mirrors
__________ refers tot he change in perceived frequency that occurs when a wave source and its observer move towards or away from each other.
the Doppler effect
the ________________ is the point where the center of mass would be if the object had a uniform density
the center of buoyancy
_____________ occurs when a thin layer of a substance is placed between two layers of another substance that has a different index of refraction
thin film interference
a _________ is a lens whose maximal thickness is small relative to the radius of curvature, object distance and image distance.
thin lens
a ___________ such as the wave on a string, is one in which the medium is displaced perpendicularly to the direction of wave propagation.
transverse wave
a group of streamlines makes up a 3d _____________
tube of flow
_______ means that the velocity at any fixed point in the fluid may vary with time.
turbulence
__________ is a flow regime characterized by chaotic property changes.
turbulence
just beyond the visible spectrum on the smaller wavelength side is ____________
ultraviolet
a _______________ shared equally by all the molecules at a given location in a fluid
uniform translational motion
virtual images are always __________
upright
the difference in pressure experienced by points closest to and farthest from the surface creates the ____________
upward buoyant force.
______ is a measure of a fluid's temporal resistance to forces that are not perpendicular to its surface.
viscosity
when an object is fully submerged, ________ are equal
volume
period of a wave is determined by what
wave source
______ is the distance from any point on a wave to the point where the wave begins to repeat
wavelength
__________ of a wave is the distance from any point in the wave to the point where the wave begins to repeat itself.
wavelength (λ)
diffraction is significant when the size of an object or opening is small relative to the ____________
wavelength of a wave
________ is the gravitational force that an object experiences when it is close to a much larger body, such as the earth.
weight
In regards to Hooke's law, all solids violate it at some limit of displacement, unique to each object. The point of violation is called the ________________. when an object is deformed past its ______________, it loses the ability to regain its original shape.
yield point yield point
two forces that are equal in magnitude but opposite in direction will cancel each other out, leaving a _________
zero net force
a __________ is a cyclical pathway for moving charge.
circuit
what two types of forces are involved in capillary action
cohesive forces adhesive forces
lenses and mirrors are categorized as _________ or _________
convergers or divergers
light bends in only what 3 ways
1. refraction 2. reflection 3. diffraction
what are the 4 types of forces in nature?
1. strong nuclear force 2. the weak nuclear force 3. gravitational force 4. electromagnetic force
a ___________ has magnitude and direction., but a ________ has magnitude only
1. vector 2. scalar
what is the index of refraction for glass
1.5
how do you solve for intensity level
10 log (I / I(subzero) I(subzero) is the threshold intensity of human hearing
A spring powered dart-gun fires a dart 1 m vertically into the air. In order for the dart to go 4 m, the spring would have to be depressed: A. 2 times the distance B. 3 times the distance C. 4 times the distance D. 8 times the distance
A. 2 times the distance This is a proportion problem. Set the elastic potential energy equal to the final energy, 1/2Kx^2 = mgh, and notice that the square of the displacement of the spring is proportional to the height. Thus, increasing the height by a factor of four requires increasing the displacement of the spring by a factor of two
If the distance between two point charges is increased by a factor of 3, the new force on either charge will: A. decrease by a factor of 4 B. decrease by a factor of 2 C. remain the same D. increase by a factor of 2.
A. decrease by a factor of 4. The force is given by Coulomb's law, F = (kqq) / r^2. The electrostatic force changes with the square of the distance between the centers of charge. In this case, 3^2 = 9. The force and the distance are inversely related. If the distance is increased the force must decrease, so answer choices C and D are correct.
An MRI has a magnetic field of 1.5 T. What force does the MRI have on a hydrogen ion at rest in the human brain? A. 0 N B. 1.5 N C. 15 N D. 150 N
A. 0 N The force on a charge moving in a magnetic field due to a magnetic field is F = qvb sinθ
A telephone pole stands as shown below. Line A is 4 m off the ground and line B is 3 m off the ground. The tensions to line A and B are 200 N and 400 N respectively. What is the net torque on the pole? A. 0 Nm B. 400 Nm C. 800 Nm D. 2000 Nm
A. 0 Nm Because the pole is not experiencing rotational motion, it can be inferred that the pole is not experiencing any net torque. If the tensions in lines A and C were the only forces acting on the pole, it would experience a net torque equal to the difference between the torque exerted by line C and the torque exerted by line A. Torque = (400 N)(3 m) - (200N)(4m) = 1200Nm - 800Nm = 400 Nm in the clock wise direction. However, because the pole "stands" and does not move, it can be inferred that the ground is exerting a force on the pole such that it experiences a net torque of 0 Nm
How much force is required to life a 10 kg box such that it is accelerated from rest to a velocity of 5 m/s within 1 second A. 150 N B. 100 N C. 50 N D. 0 N
A. 150 Draw the free body diagram for the box. There are two forces acting on the box: the force of gravity, 10kg x 10 m/s^2 = 100N downwards, and the force lifting the box upwards, F-lift. In order to accelerate the box upward, the upward force must be greater than the downward force. Choice A is the only option greater in magnitude than the downward force of gravity. To solve the exact value, use kinematics and force equations. The acceleration of the box is (Vf-Vi)/time = (5 m/s - 0 m/s)/ 1s = 5 m/s^2. Since the box is accelerating upward, we set the upward and downward forces equal to each other and add ma to the downward force
For a point charge, the electric field is found by which formula
E = K (q1) ____ r^2 Done by dividing coloumb's law by q
A meteor with a mass of 1 kg moving at 20 km/s collides with Jupiter's atmosphere. The meteor penetrates 100 km into the atmosphere and disintegrates. What is the average force on the meteor once it enters jupiters atmosphere? A. 2 x 10^3 N B. 4 x 10^3 N C. 8 x 10^3 N D. 2 x 10^5 N
A. 2 x 10^3 N The question stem indicates that, at disintegration, the velocity of the meteor is 0 m/s. The frictional force acts on the meteor such that its velocity decreases from 20 km/s to 0 m/s. That is , the force does work equal to ΔKE of the meteor. W = Fd = F (100 km) = 1/2 mv(final)^2 - 1/2 mv(initial)^2 = 1/2 (1 kg)(20km/s)^2 -1/2(1kg)(0 km/s)^2. F =[ 1/2 (400 x 10^6 kg m s^-2)]/(100 x 10 ^3 m) = 2 x 10^3 N
A cell at rest has a potential of -70 mV across it's membrane. Assume the diameter of the cell is 20 micrometers. The cell membrane has a capacitance of 1 microF / cm ^2 Elementary charge = 1.6 x 10^-19 C. How much energy is stored in one square centimeter of the cell membrane? A. 2.5 x 10^-9 J/cm^2 B. 3.5 x 10^-8 J/cm^2 C. 3.5 x 10^3 J/cm^2 D. 3.5 x 10^8 J/cm^2
A. 2.5 x 10^ -9 J/ cm^2 Use any of the equations for energy stored in a capacitor U = 1/2 CV^2 = (1/2)(1μF/cm^2)( 70 mV)^2 = (1/2)(10^-6 F/cm^2)( 7 x 10^-2 V)^2 = 2.5 x 10^-9 J/cm^2
A hiker throws a rock horizontally off a cliff that is 40 meters above the water below. If the speed of the rock is 30 m/s, how long does it take for the rock to hit the water? A. 3 sec B. 4 sec C. 5 sec D. 6 sec
A. 3 seconds Horizontal speed has no effect on the length of time that a projectile is in the air, so it can be ignored for this question. Because the initial vertical speed is zero, use the equation x = (1/2)gt^2 to solve for time with x=40m and g = 10 m/s^2. Another approach is to reason that the rock will lose 10 m/s of velocity every second, taking 3 seconds for the rock to go from 30 m/s to 0 m/s
The pressure at the bottom of a cylindrical tube filled with water was measured to be 5000 Pa. If the water in the tube were replaced with ethyl alcohol, what would be the new pressure at the bottom of the tube? (The density of ethyl alcohol is 0.8 g/cm^3.) A. 4000 Pa B. 4800 Pa C. 5000 Pa D. 6250 Pa
A. 4000 Pa The formula for fluid pressure is P = pgh. If the density is changed, the pressure will change by the same ratio. Since the specific gravity of ethyl alcohol is 0.8, the pressure will change by the same ratio. Since the specific gravity of ethyl alcohol is 0.8, the pressure will decrease by a factor of 0.8. 5000 Pa x 0.8 = 4000 Pa. Replacing the fluid with a less dense or lighter fluid must lower the pressure, so answer choice D can be eliminated. By remembering that pressure depends on density, C can be eliminated as well.
Each of the resistors in the circuits below represents a light bulb. If all three circuits use the same size battery, which circuit will produce the most light? I. has one resistor II. has two resistors in serial III. has 3 resists, two in parallel with each other A. I only B. II only C. III only D. I, II, III will produce same amount of light
A. I only The energy for the light comes from the battery. The rate at which the energy is released is the power. P = (i^2)R. Since the voltage remains constant, the change in the current will produce the greatest change in the power. Where more light bulbs are attached, the resistance goes up and the current goes down; thus the power goes down and less light is produced. Circuit I has the least resistance in the circuit and will draw the most current from the battery.
Which of the following statements is (are) true? I. virtual images can be projected onto a screen II. Real images can never be seen III. Real images can only be created by converging lenses and concave mirrors in a single lens or single mirror A. III only B. I and II only C. I and III only D. I, II, and III
A. III only A virtual image is formed by an apparent, rather an actual convergence of light. Projecting an image onto a screen requires projection of the light that forms that image. Because no light rays form a virtual image, virtual images cannot be projected onto screens. Therefore, I is a false statement, and choices B, C, and D can be eliminated. Choice A, III only, must be the correct answer choice by process of elimination.
Two particles are held in equilibrium by the gravitational and electrostatic forces between them. Particle A has mass Ma and charge Qa. PArticle B has mass Mb and charge Qb. The distance between the charges is d. Which of the following changes would cause the charges to accelerate towards one another. A. Ma is doubled and Mb is doubled B. Ma is doubled and Mb is halved C. Qa is doubled and Qb is doubled D. d is doubled
A. Ma and Mb is doubled Since gravitational force is attractive, the electric force must be repulsive. Doubling both masses will increase the gravitational force. Chocie C is wrong because doubling both charges will increase the repulsive electric force. Chocie B will not change the gravitation force as doubling one mass and halving the other cancels each other out. Chocie D will will affect both force equally and thus not change the balance they create on particles
In order for white blood cells to leave the circulation and enter tissues, they must roll along the wall of the blood vessel. Which of the following is true regarding the white blood cell rolling? A. blood is a non-ideal fluid so the velocity of the blood is less at the wall of the vessel than in the center of the vessel. B. Blood is an ideal fluid so the velocity of the blood is less at the wall of the vessel than in the center of the vessel. C. blood is an ideal fluid so the velocity of the blood is greater at the wall of the vessel than in the center of the vessel. D. blood is a non-ideal fluid so the velocity of the blood is greater at the wall of the vessel than in the center of the vessel.
A. blood is a non-ideal fluid so the velocity of the blood is less at the wall of the vessel than in the center of the vessel. In order for white blood cells to roll along the wall of the vessel, they must be moving slower along the wall. In an ideal fluid we assume that the velocity of the fluid through a cross-section is constant. Answer B and C are incorrect because the velocity cannot be different at different points in the same cross-section of an ideal fluid.
The electric field for the two point charges A and B is shown below. Which of the following is true? (A and B both have arrow pointing away from each other) A. both charges are positive B. both charges are negative C. the charges have opposite signs D. the signs of the charges cannot be determined
A. both charges are positive. The field lines are directed away from both charges, so by definition they are both positively charged. If they were both negative, as in answer choice B, the field lines would be directed towards each charge. If they had opposite signs, the field lines would go from one charge, the positive charge, to the other, the negative charge
A 1 cm stands 4 cm in front of a concave mirror with a 2 cm focal distance. The image is: A. inverted and 1 cm tall B. inverted and 2 cm tall. C. upright and 1 cm tall D. upright and 2 cm tall.
A. inverted and 1 cm tall. Convcave mirrors are converging mirrors. Converging mirrors form real, inverted images of objects outside their focal points. The focal distance of the mirror is 2 cm and the object is placed 4 cm in front of the mirror. Therefore, the object is outside the focal point, and the image of the object formed by the mirror is inverted. Answer choices C and D, which state the image is upright, can be eliminated. According to the thin lens equation, 1/f = 1/d0 + 1/di. By convention, focal distances of converging mirrors are positive and object distances of objects on the same side of the mirror are positive. therefore, 1/di = 1/f-1/do = 1/(+2cm) - 1/(+4cm) = 1/4 cm and di = 4 cm. Magnification, m =-di/do = hi/ho = -(4 cm)/(4cm) = -1. Since the magnification has a magnitude of 1, the image height is the same as the object height, 1 cm. The negative sign confirms that the image is inverted. Thus A is the best answer choice.
A spigot was opened at the bottom of a barrel full of water and the water was allowed to run through the spigot until the barrel was empty. Which of the following describes the speed of the water flowing through the spigot as the barrel emptied. A. always decreasing B. always increasing C. constant D. decreasing, then increasing
A. is correct The equation governing the velocity is v = Square root (2gh) as h decreases, so does v
If 1 kg blocks were stacked one upon the other starting at the surface of the earth and continuing forever into space, the blocks near the bottom of the stack would have: A. less gravitational potential energy than blocks at the middle or blocks near the top of the stack B. less gravitational potential energy than blocks at the middle and the same gravitational energy as blocks near the top of the stack C. the same gravitational potential energy as all other blocks D. more gravitational potential energy than blocks at the middle or blocks near the top of the stack.
A. less gravitational potential energy than blocks at the middle or blocks near the top of the stack. According to Newton's law of universal gravitation, the force of gravity is equal to (GmM)/r^2. Gravitational potential energy is commonly said to equal F(g)r, or GmM/r. And, indeed, when gravitational force is nearly constant, as near the surface of the earth, gravitational potential energy is equal to the product of the force of gravity exerted by the earth on an object and the distance from the center of the object. However, strictly speaking, gravitational potential energy is equal to the area under the curve of gravitational force as a function of distance, r. Therefore, even as the magnitude of gravitational force exerted on a block decreases, its potential energy nonetheless increases. In non-calculus based physics, it is said that as an object moves from the surface of the earth to infinity, the value of its potential energy increases from a large negative number to zero. Recall that each movement against the force of gravity requires work and contributes the potential energy of an object. Therefore blocks at the middle or top of the stack will have greater potential energy than those at the bottom of the stack.
If the intensity of a sound is doubled, the decibel level will increase by: A. less than 10 dB B. exactly 10 dB C. more than 10 dB D. exactly 20 dB
A. less than 10 dB Decibel level, or intensity level, is related to intensity by a logarithmic scale. If the intensity is doubled, decibel level increases by about 3 dB; choice A is correct. Remember that an increase in intensity level of 10 dB means that intensity has increased by a factor of 10.
A girl riding her bicycle up a steep hill decides to save energy by zigzagging rather than riding straight up. Ignoring friction, her strategy will: A. require the same amount of energy but less force on the pedals. B. require the same amount of energy and the same amount of force on the pedals. C. require less energy and less force on the pedals. D. require less energy and more force on the pedals.
A. require the same amount of energy but less force on the pedals. While riding her bicycle up the hill, the rider applies a force to her bicycle pedals that is translated into the force required to counteract the force of gravity and propel the bike and rider a given distance up the hill. By zigzagging, the rider increases the distance over which she travels. However, she also decreases the incline at which she travels. In doing so, she reduces the force of gravity she must oppose in order to climb the hill. Recall that the force of gravity that accelerates an object down an incline is equal to mg sinθ. Therefore, if, by zigzagging, she were to reduce the incline from 30° to 15°, she would decrease the downward force of gravity from mg sin30° to mgsin15°. Thus less force would need to be applied to the pedals; choices B and D, which suggest that equal or greater force would need to be applied, can be eliminated. Because work is path independent, the amount of energy required to ascend the hill would would remain equal to mgh, where h is the vertical displacement of the rider and her bike. Therefore, C can be eliminated and A is the best answer. Think of each zigzag path as a ramp that decreases the force required to do a given amount of work by increasing the distance over which it is applied.
What is the net force on the dipole inside the capacitor if the plates are separated by 1 cm? A. 0 N B. 4 N C. 8 N D. 16 N
A. the electric field inside a capacitor is constant. By definition, a dipole has equal but opposite charges on either end. The force on each end of the dipole is Eq and in opposite directions. The net force is zero.
A box rests on an incline. Which of the following describes the forces on the box as the angle of inclination is increased? A. the force parallel to the ramp increases and the force perpendicular to the ramp decreases. B. The force parallel to the ramp increases and the force perpendicular to the ramp also increases C. the force parallel to the ramp decreases and the force perpendicular to the ramp also decreases D. the force parallel to the ramp and the force perpendicular to the ramp remain constant
A. the force parallel to the ramp increases and the force perpendicular to the ramp decreases The force parallel to the ramp is the force down the incline, mgsinθ. As the angle of inclination increases, sinθ increases and so does the force parallel to the ramp. The force perpendicular to the ramp is the same as the normal force, mg cosθ. As θ increases, cosθ decreases, and so does the normal force. Another approach is to imagine the most extreme situation where the angle is 90degrees and the box is sitting against a wall. In this case the force parallel to the ramp would be large and the box would be in free fall.
An aneurysm is a localized bulge in the wall of a blood vessel. Is the pressure in the aneurysm higher or lower than the pressure in the normal vessel? A. The pressure is higher in the aneurysm because it has a greater cross-sectional area than the normal blood vessel. B. The pressure is lower in the aneurysm because it has a greater cross-sectional area than the normal blood vessel. C. The pressure is higher in the aneurysm because flow speed is higher in the normal blood vessel. D. The pressure is lower in the aneurysm because flow speed is higher in the normal blood vessel.
A. the pressure is higher in the aneurysm because it has a greater cross-sectional area than the normal blood vessel. The aneurysm has a greater radius than the normal blood vessel. Thus, it will also have a greater cross-sectional area (A = pi r ^2). The blood in the aneurysm will have a lesser velocity due to this greater cross-sectional area (Q = Av), eliminating answer choices C and D. By Bernoulli's equation (assume constant height), if the velocity is decreased, the 'velocity head' will also be decreased. and the pressure term will increase. Thus, the pressure is higher in the aneurysm.
The coma cluster is a galaxy approximately 2.7 x 10^15 km away from earth. How many years does it take for light from the coma cluster to reach earth? (Note: light travels at approximately 3 x 10^8 m/s) A. (2.7x10^15/1)* (1/ 3x10^8)* (1/60)*(1/60)*(1/24)*(1/365)*(1000/1) B. (2.7x10^15/1)* (1/ 3x10^8)* (1/60)*(1/24)*(1/365)*(1000/1) C. (2.7x10^15/1)* (3x10^8 / 1)* (1/60)*(1/24)*(1/365)*(1000/1) D. (1/ 2.7 x 10^15)*(3 x 10^8/1)*(60/1)*(60/1)*(24/1)*(365/1)*(1000/1)
A. use the units to convert km and m/s to years km x (s/m)x(min/s)x(hrs/min)x(days/hrs)x(yrs/days)x(m/km)
Water in moist soil rises through capillary action. The intermolecular forces between water molecules are: A. weaker than the intermolecular forces between water and soil molecules. B. equal to the intermolecular forces between water and soil molecules C. stronger than the intermolecular forces between water and soil molecules D. the comparative strength between the intermolecular forces cannot be determined with the information given.
A. weaker than the intermolecular forces between water and soil molecules Since the water is rising, it is somehow pulled up against gravity. The answer choices allow for only one explanation: The water must be grabbing the walls (the soil) around it and pulling itself upward. This 'grabbing' is an intermolecular bond between water and the soil. IF it were weaker than the bond between water and water, then the water be pulled back onto itself
A skydiver jumping from a plane will accelerate up to a maximum velocity and no greater. This constant velocity is known as terminal velocity. Upon reaching terminal velocity, the net force on the skydiver is: A. zero and the skydiver is in equilibrium B. zero and the skydiver is not in equilibrium C. equal to the weight of the skydiver and the skydiver is in equilibrium D. equal to the weight of the skydiver and the skydiver is not in equilibrium
A. zero and the skydiver is in equilibrium The question stem indicates that the skydiver has reached a constant, terminal velocity. Therefore, the skydiver experiences no acceleration. Remember that, in the absence of acceleration, there can be no net force. Therefore, the net force is zero and answer choices C and D can be eliminated. To decide between choices A and B, recall that equilibrium can be either static or dynamic. That is, equilibrium requires constant velocity, not necessarily zero velocity. The skydiver is in dynamic equilibrium, meaning that choice A is the best choice.
___________ indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.
Archimedes' principle
The mechanical advantage for a machine is define as the output force divided by the input force. Since the output force is typically greater than the input force, this value is normally greater than one. For an ideal machine, what would be another way of representing the mechanical advantage? A. (output distance)/(input distance) B. (input distance)/(output distance) C. (output distance) x (input distance) D. (input distance) + (output distance)
B. (input distance)/(output distance) The formula relating work done on and by machines is F(input)d(input) = F(output)d(output), where d is the distance over which the input and output forces act. If mechanical advantage is equal to (output force)/(input force), then it must also be equal to (input distance)/(output distance)
What is the energy required to operate a 60 W light bulb for one minute? A. 1 J B. 60 J C. 360 J D. 3600 J
D. 3600 J A Watt is a joule/sec. Solve for joules by multiplying power and time. Don't forget to convert time to seconds. So (60 W)(60 Sec) = 3600 J
electromagnetic forces require the presence of a _______ object or magnet
charged
The frictionless pulley system below reduces the force necessary to lift any mass by a factor of 3. How much power is required to lift a 30 kg object 2 meters in 60 seconds using this pulley system? A. 4 W B. 10 W C. 24 W D. 120 W
B. 10 W Like all ideal machines, the pulley changes only the force required to do a given amount of work in a given amount of time. It does not change either the amount of work done or the time during which the force acts. Recall that power is change in energy per unit time. In this case, ΔE = W= Fd = mgh = (30 kg)(10 m/s^2)(2 m) = 600 J. therefore, P= ΔE/t = (600 J)/(60s) = 10 J/s = 10 W. therefore B is the correct answer
The sound level of the chirping made by a brid at a distance f 5 meters is measured at 30 dB. When the same bird is 50 meters away the sound level is measured at 10 dB. How many times greater is the amplitude of the sound wave at 5 meters away compared to 50 meters away? A. 3 times greater B. 10 times greater C. 20 times greater D. 100 times greater
B. 10 times greater Intensity level is related to intensity by a logarithmic scale: intensity level equals ten times the log of intensity. Therefore, an increase of 20 dB equals a 100-fold increase in intensity. Also, intensity is proportional to the square of amplitude, so a 100-fold increase in intensity is due to a 10-fold increase in amplitude
A positively charged particle starts at rest 25 cm from a second positively charged particle that is held stationary throughout the experiment. The first particle is released and accelerates away from the second particle. When the first particle has moved 25 cm, it has reached a velocity of 10 m/s. What is the maximum velocity the first particle will reach? A. 10 m/s B. 14 m/s C. 20 m/s D. the first particle will never stop accelerating and will reach an infinite velocity
B. 14 m/s This problem is about energy. The system has a total electric potential energy of U = kqq / r. Remember, the forces acting are conservative so mechanical energy is conserved. Thus, as the first particle is propelled away from the second, electric potential energy is conserved. Thus, as the first particle is propelled away from the second, electric potential energy is converted to kinetic energy. When the first particle moves 25 cm, it has doubled its distance of separation. From U = kqq/r, the first particle has lost half of its potential energy to kinetic energy when r is doubled. When the first particle is infinitely far from the second particle, it will have lots the rest of the electric potential energy to kinetic. In other words, it will have twice the kinetic that it had at 25 cm. From K.E. = 1/2 mv^2, if K.E. is multiplied by 2, the velocity must be multiplied by the square root of 2, or approximately 1.4. 1.4 x 10 = 1.4 m/s.
Each resistor in the circuit below has a resistance of 2 Ω. The battery is a 12 V battery. What is the current across resistor B? A ___________/\/\/\__________ I____________/\/\/\_________I _ B > T >C I__________________________I A. 1 A B. 2 A C. 3 A D. 4 A
B. 2 A The effective resistance is 3 Ω. First, find the effective resistance of the two resistors in parallel, resistor A and resistor B. 1/2 Ω + 1/2 Ω = 1/Rtotal Then attribute this resistance to a single resistor in series with resistor C and find the overall effective resistance. 1 Ω + 2 Ω = 3 Ω The voltage divided by the effective resistance gives 4 amps coming out of the battery. The 4 amps split evenly at the node before A and B
A one meter board with uniform density hangs in static equilibrium from a rope with tension T. A weight hangs from the left end of the board as shown. What is the mass of the board? I 0.2 m I <------------> I ____________I___________________________________ I __I______ I__3kg__I A. 1 kg B. 2 kg C. 3 kg D. 4 kg
B. 2 kg The axis of rotation is the point where the rope attached to the board. The hanging weight creates a counter-clockwise torque equal to 3 kg x 0.2 m. The weight of the board creates a clockwise torque at the distance from the rope attachment to the boards center of mass, which is 0.3 m. The net torque is zero, so the clockwise torque equals the counterclockwise torque, so 3 kg x 0.2 m = 0.3 m times the weight of the board. Therefore the weight of the board is 2 kg
The diagram below shows two different masses hung from identical Hooke's law springs. The hooke's law constant k for the springs is equal to: Spring on the left is stretched 6 cm with a weight of 1 kg attached spring on the right is stretched 7 cm with a weight of 1.5 kg attached A. 2 N/cm B. 5 N/cm C. 10 N/cm D. 20 N/cm
B. 5 N/cm The initial displacements of the springs are unknown, but it can be assumed that they were the same for both masses. The spring displaces an extra 1 cm when an additional 5 N of force is added. to solve for the spring constant, these numbers can be substituted into Hooke's Law. K=F/x = (5 N)/(1 cm) = 5 N/cm
The index of refraction of glass is 1.5. How long does it take for light to pass through a plate of glass that is 1 cm thick? A. 5 x 10^-8 s B. 5x10^-11 s C. 2 x 10^-8 s D. 2 x 10^-11 s
B. 5 x 10^-11 s We can find the speed of light through glass by using the index of refraction. n = (c/v) or v = (c/n) = (3x10^8)/1.5 = (2x10^8) Once we know the speed of light in glass, we can use x=vt. Rearrange the equation to solve for t and change cm into meters. t = (1x10^-2)/(2 x 10^8) = 0.5 x 10^-10 = 5x 10^-11
Neurons send messages via electrical impulses along their axons. The impulse, called an action potential, is propagated when ions enter or exit the cell. Approximately 5.5 x 10^11 Na+ ions per meter cross the cell membrane during a second of the propagation of an action potential. What is the current caused by the flow of Na+ across 1 cm of the axon? (elementary charge=1.6 x 10^-19 C) A. 5.5 x 10^ 9 C/s B. 8.8 x 10^-10 C/s C. 5.5 x 10^-9 C/s D. 8.8 x 10^-9 C/s
B. 8.8 x 10^-10 C/s Remember to use the units. The flow of Na+ ions per meter of axon per second is 5.5x 10^11. The flower of Na+ ions in one centimeter of axon is: (5.5 x 10^11 Na+ ions / meter)(1 meter/10^2 cm) = 5.5 x 10^9 Na+ ions/cm/sec Each Na+ ion has a charge equal to the elementary charge, the charge of one proton. The total charge flowing across one second is: (5.5 x 10^9 Na+ ions/sec)(1.6 x 10^-19 C/ Na+ ion) = 8.8 x 10^-10 C/s
When -10 C of charge are moved from point A to point B in the diagram below, 90 J of work is done. The voltage between point A and point B is: A. 0.9 V B. 9 V C. 90 V D. 900 V
B. 9 V Electrostatic forces are so conservative, so the work done by a force against them is conserved in potential energy. A volt is a joule / coloumb, so voltage can be determined by dividing work by charge. (90 J) / (10 C) = 9 J/C = 9 V. choice B is correct
newton's second law can be written as which equation
F=ma
The force in an electric field is calculated using which formula
F=qE
Which of the following describes a situation requiring no net force? A. a car starts from rest and reaches a speed of 80 km/hr after 15 seconds B. a bucket is lowered from a rooftop at a constant speed of 2 m/s C. a skater glides along the ice, gradually slowing from 10 m/s to 5 m/s D. the pendulum of a clock moves back and forth at a constant frequency of 0.5 cycles per second
B. a bucket is lowered from a rooftop at a constant speed of 2 m/s. Acceleration requires net force. There, the answer is the that one that describes movement in the absence of acceleration. In the absence of acceleration, velocity is constant. choices A and C explicitly describe changes in velocity and therefore can be eliminated. Choice D describes the movement of a pendulum at constant frequency. Recall that the force of gravity acts on a pendulum during its motion, causing it to accelerate such that its potential energy is converted into kinetic energy. As the pendulum approaches its equilibrium position, its velocity increases to a maximum before once again decreasing to zero. Since the pendulum experiences acceleration, it must experience a non-zero net force; D can be eliminated. A bucket lowered at a constant speed of 2 m/s experiences no acceleration and therefore, no net force. B is the best answer
A glass magnifying lens is submerged in water to view an underwater object. Compared to viewing the object with the magnifying lens out of water, this will: A. increase the magnification B. decrease the magnification C. not change the magnification D. the magnifying glass will not work at all under water
B. decrease the magnification Remember that lenses do what they do because they refract, or bend, light. A magnifying lens creates images of objects that are larger than the objects, themselves, by bending the light from those objects. The extend to which light bends as it passes from one medium to another depends on the extent to which the speed of light changes as it passes between those media. Recall that refractive index, n, of medium is a measure of the extent to which the speed of light changes. n = c/v, where c is the speed of light in a vacuum and v is the speed of light in the medium. According to Snell's law, n1sinθ1 = n2 sinθ2. Therefore, as n2 approaches n1, θ2 approaches θ1. In other words, light bends less when it passes between media with similar indices of refraction than it does when it passes between media with dissimilar indices of refraction. The indices of refraction of air, water, and glass are approximately 1, 1.3, 1.5 respectively. As the magnifying lens (n=1.5) moves from air (n=1) to water (n=1.3) its index of refraction approaches the index of refraction of the surrounding medium. Therefore the light is bent less and magnified less. thus b is the bester answer choice.
Which of the following is true of blood pressure measurements taken in a person standing upright? Assume the blood vessels in the arms and legs have the same radius. A. blood pressure is greater in the arms B. blood pressure is greater in the legs C. blood pressure is the same in the arms and legs D. the answer cannot be determined from the information given.
B. is correct Use Bernoulli's equation to solve this problem Since the surface area of the two vessels is equal, the velocity of the blood will be equal as well. Thus the velocity head term, 1/2 pv^2, will be the same in the arm and the leg leaving, P(arm) + pgh(arm) = P(leg) + pgh(leg) The arm is higher than the leg, so the 'elevation head' term will be greater, pgh(arm) > pgh(leg). To balance this the pressure term P(arm) will be less than that of the leg P(leg). Blood pressure is slightly higher (<10 mmHg) in the legs than in the arms if the person is standing. Another approach to this problem is to think of the body as a column of blood. When standing, the blood in the legs must support all of the blood above it, therefore the pressure will be higher
An eccentric pulley can be used on a compound bow to increase the velocity of an arrow. The pulleys pivot around the dots as shown. Below is a compound bow in two positions. The tension at point A compared to point b is most likely: (refer to page 54) A. less in both position 1 and position 2 B. less in position 1 and greater in position 2 C. greater in both position 1 and position 2 D. greater in position 1 and less in position 2
B. less in position 1 and greater in position 2 Because the points of rotation of eccentric pulleys are off-center, they function as modified levers. notice that, in position 1, the distance from point A to the point of rotation of the top pulley is greater than the distance from point B to the point of rotation of the bottom pulley. Therefore, in position 1, the lever arm for the tension at point A is greater than that for the tension at point B. The components of the compound bow are stationary, then the sum of the torques acting on the components must be zero and the tension at point A must be less than the tension at point B. Therefore, choices C and D can be eliminated. In position 2, the distance from point A to the point of rotation of the top pulley is less than the distance from point B to the point of rotation of the bottom pulley. Therefore, if the components of the bow are stationary, then the tension at point A must be greater than the tension at point B. Thus choice A can be eliminated and choice B is the best answer.
Two drops of equal volume of different substances were placed on the same flat surface. A side view of drop A and drop B is shown below /----------\ I A I _______________ _________\________/_______/_______B_________\________ A. stronger intermolecular forces and lesser surface tension B. stronger intermolecular forces and greater surface tension C. weaker intermolecular and lesser surface tension D. weaker intermolecular forces and greater surface tension
B. stronger intermolecular forces and greater surface tension The drop with stronger intermolecular forces will have greater surface tension, which will cause it to bead up more. Drop A is beaded up more in this example so it will have stronger intermolecular forces, eliminating answer choices C and D
Newton's third law states that for every action there exists an equal and opposite reaction. What is the force that acts in reaction to the force of Earth's gravity on an object on its surface? A. the normal force that the object exerts on the earth. B. The force of gravity that the object exerts on the Earth C. the normal force that the Earth exerts on the object D. the force of gravity that the Earth exerts on the object
B. the force of gravity that the object exerts on the earth Newton's third law refers to the same type of force acting between two objects. In this case, the earth exerts a force of gravity on an object and the object exerts an equal and opposite force on the Earth. choice A is incorrect because the normal force is not always equal in magnitude to the force of gravity. For example, the normal force on an inclined plane. Choice C and D are incorrect because the reaction force would be exerted by the object on the Earth.
An inverted image is created 5 m in front of a mirror. Which of the following could be true about the mirror and the object? A. the mirror is convex with less than a 5 m focal distance. B. the mirror is concave with less than a 5 m focal distance C. the mirror is convex with more than a 5 m focal distance D. the mirror is concave with more than a 5 m focal distance.
B. the mirror is convex with less than a 5 m focal distance The question stem states that the mirror forms an inverted image. Only converging mirrors can form inverted images. Converging mirrors are concave mirrors. Therefore, choices A and C, which state that the mirror is convex, can be eliminated. Converging mirrors only form inverted images of objects positioned beyond their focal points. Therefore, since the object distance is 5 m, the focal distance must be less than 5 m. Therefore, D , which states that the focal distance is greater than 5 m, can be eliminated. Choice B is the best answer
A winch is used to lift heavy objects to the top of building under construction. A winch with a power of 50 kW was replaced with a new winch with a power of 100 kW. Which of the following statements about the new winch is NOT true? A. the new winch can do twice as much work in the same time as the old winch. B. the new winch takes twice as much time to do the same work as the old winch. C. the new winch can raise objects with twice as much mass at the same speed as the old winch. D. the new winch can raise objects with the same mass at twice the speed of the old winch.
B. the new winch takes twice as much time to do the same work as the old winch. P = ΔE / t In this instance, change in energy is equal to work done and P=W/t. Notice that power and work are directly proportional to one another. If P is doubled from 50 kW to 100 kW, then the work done in a given amount of time is also doubled. Therefore, choice A is a true statement and can be eliminated. Notice that, in this case, W=mgh, and W is directly proportional to m. C states that the new winch can raise an object with a mass of 2m in the same amount of time that the old winch can raise a mass of m. This makes sense since the new winch can do twice as much work in a given amount of time. D suggests that , if the old winch can do work W in time t, then the new winch can do work W in time t/2. Again, this makes sense given that the new winch has twice the power of the old winch. D can be eliminated. B however indicates that the power of the new winch is half that of the old winch. Therefore, it is a false statement. making B the best answer
A crate is to be lifted to a height of 3 meters with the assistance of an inclined plane. If the inclined plane is a non-ideal machine, which of the following statements is most likely true? A. the non-ideal inclined plane increases the force required and decreases the work that has to be done. B. the non-ideal inclined plane decreases the force required and increases the work. C. the non-ideal inclined plane increases the force and the work required. D. the non-ideal inclined plane decreases the force and the work required.
B. the non-ideal inclined plane decreases the force required and increases the work. Both ideal and non-ideal machines reduce the force required to perform a task; choices A and C can be eliminated. An ideal machine is a system in which work done on the machine by an applied force is transferred, undiminished, into work done by the machine on the surroundings. Therefore, an ideal machine reduces the force required without changing the work required. By contrast, a non-ideal machine is a system in which some of the energy transferred as work done on the machine is lost to friction, deformation, and/or other inefficiencies. Therefore, more work is required than would be in the absence of the machine. Thus a non-ideal machine reduces the force required but increases the work required. choice D can be eliminated and choice B is the best answer
One end of a string is shaken each second, sending a wave with an amplitude of 10 cm toward the other end. The string is 5 meters long, and the wavelength of each wave is 50 cm. How many waves reach the other end of the string in each 10 second interval. A. 2 B. 5 C. 10 D. 50
C. 10 waves. The frequency of the waves being sent is equal to the frequency of the waves being received. Every second, one wave is sent. In 10 seconds, 10 waves are sent. The other information is extraneous
Atherosclerosis is a vascular disease associated with the development of plaques, which are fatty masses of tissue. Assume that blood flows through a healthy artery at a speed of 0.5 m/s. IF a plaque were to decrease the radius of that artery by 40%, at what speed would blood flow through it? A. 0.5 m/s B. 1.0 m/s C. 1.4 m/s D. 2.0 m/s
C. 1.4 m/s see page 222
Two charged metal plates are placed one meter apart creating a constant electric field between them. A one coulomb charged particle is placed in the space between them. The particle experiences a force of 100 Newtons due to the electric field. What is the potential difference between the plates? A. 1 V B. 10 V C. 100 V D. 1000 V
C. 100 V This is a units question. 100 N/C is equivalent to 100 V/m. The one coulomb experiences 100 N of force. This is a measure of the strength of the electric field: 100 N/C. Another way to say 100 N/C is 100 V/m. The plates are one meter apart, so they have a 100 volt potential difference
Two identical discs sit at the bottom of a 3 m pool of water whose surface is exposed to atmospheric pressure. The first disc acts as a plug to seal the drain as shown. The second disc covers a container containing nearly a perfect vacuum. If each disc has an area of 1 m^2, what is the approximate difference in the force necessary to open the containers? (note: 1 atm = 101,300 Pa) A. there is no difference B. 3000 N C. 101,300 N D. 104,300 N
C. 101,300 The only difference between the two discs is what they are covering. ignore everything else. The first disc has atmospheric pressure pushing upward; the second disc does not. This is the difference between the forces necessary to lift them.
How much work is done by pressure to force 1 cm^3 of blood across a vessel with a pressure drop of 10^-3 atm? A. 10^-9 J B. 10^-6 J C. 10^-4 J D. 10^-3 J
C. 10^-4 J Recall that work, W, is equal to Fd, where F is a force and d is the distance over which it is applied. Recall also that pressure, P, is equal to F/A. Therefore, the equation for work can be rewritten as W = (F/A)(A)(d) = PV. Because work is the area under the graph of pressure as a function of volume, W = PΔV at constant pressure and ΔPV at constant volume. In this case, pressure changes by 10^-3 atm and volume remains constant at 1 cm^3. Note that it is the pressure gradient that drives blood through the vessel. To calculate work done in joules, convert atm to Pa and cm^3 to m^3. Because 1 atm is approximately equal to 10^5 Pa, 10^-3 atm is approximately equal to 10^2 Pa. Because 1 cm = 10^-2 m, 1 cm^3 = 10^-6 m^3. Therefore, W = (10^2)(10^-6 m^3) = 10^-4 J
an inventor designs a machine that he claims will lift a 30 kg object with the application of only a 25 N force. If the inventor is correct, what is the shortest possible distance through which the force must be applied for each meter the object is raised? A. 5 m B. 8 m C. 12 m D. 15 m
C. 12 m Again, machines decrease the force required to do a given amount of work by increasing the distance over which the is applied; they do not change the work required. Therefore, W=Fd=mghand d =mgh/F. Because the question stem asks for distance over which the force is applied per meter that the object is raised, assume that h, the distance that the object is raised, is equal to 1 m. Therefore, d = p(30 kg)(10 m/s^2)(1m)] / (25 N) = (300 J)/(25N) = 12 m
A weather balloon travels upward for 6 km while the wind blows it 10 km north and 8 km east. Approximately what is its final displacement from tis initial position? A. 7 km B. 10 km C. 14 km D. 20 km
C. 14 km The balloon travels in 3 perpendicular directions. These can be considered 3 displacement vectors. The total displacement is the vector sum of the 3. Notice that two of the vectors have lengths of 8 and 6, which are multiples of 4 and 3. These are the components of a 3-4-5 triangle. Thus, the displacement from the tail of the 6 km vector to the head of the 8 km vector is 10 km. This 10 km vector is perpendicular to the other 10 km vector. Using the Pythagorean theorem with the 2 km vectors results in a total displacement of approximately 14 km.
If the AC current delivered to a home by the electric company is delivered at 120 Vrms, what is the maximum voltage across an outlet? A. 86 V B. 120 V C. 170 V D. 220 V
C. 170 The maximum voltage is given by Vmax = √(2) (Vrms) Vmax = √(2) (120V) = (1.4)(120V) = 168 V which rounds to 170 V
A brick with a density of 1.4 x 10^3 kg/m^3 is placed on top of a piece of Styrofoam floating on water. If one half the volume of Styrofoam sinks below the water, what is the ratio of the volume of the Styrofoam compared to the volume of the brick? Assume that the Styrofoam is massless. A. 0.7 B. 1.4 C. 2.8 D. 5.6
C. 2.8 The density of the brick is 1400 kg/m^3. The density of water is 1000 kg / m^3. In order to float, the brick must displace an amount of water equal to its weight. The density of the brick is 1.4 times that of water, so an amount of water 1.4 times the volume of the brick must be displaced. One half of the Styrofoam block is required to displace this water, so the volume of the water displaced is equal half the volume of the Styrofoam and is also equal to 1.4 times the volume of the brick. Thus, 0.5 V Styrofoam = 1.4 V(brick). Multiplying both sides by 2 results in Volume of Styrofoam = 2.8 Volume of brick
A wheelchair access ramp is to be designed so that 1000 N can be lifted to a height of 1 meter through the application of 50 N of force. The length of the ramp must be at least: A. 5 m B. 10 m C. 20 m D. 100 m
C. 20 m For an inclined plane, Fd = mgh, so (50 N)d = (1000N)(1 m) and d = 20 m
A student with a mass of 40 kg sits on the end of a seesaw with a total length of 10 meters as shown in the picture. How far to right of center of the seesaw should a student with a mass of 50 kg sit to achieve the best balance? A. 1 m B. 2m C. 4 m D. 5 m
C. 4 m to balance the seesaw, the torque exerted by the 50 kg student should be equal tot he force exerted by the 40 kg student. (400 N)(5m) = (500 N)(X). So x=4, and the student should sit 4 m to the right of the seesaw center.
A child's bathtub toy has a density of 0.45 g/cm^3. What fraction of the toy floats above the water? A. 5% B. 45% C. 55% D. 95%
C. 55% Without the floating equation, the quickest way to do this problem is to take the example to the extremes. If the specific gravity of the toy were 0.999, the toy would be almost the same weight as water, and of course, only a very small part would float above the water; (0.001/1) x (100%) = 0.1%. The specific gravity must be how much is under the water. Now look at the example in the question. 45% must be under water, so 55% must be above.
A rescue helicopter lifts a 50 kg rock climber by a rope from a cliff face. The rock climber is accelerated vertically at 5 m/s^2. What is the tension in the rope? A. 350 N B. 500 N C. 750 N D. 1500 N
C. 750 N The net force on the rock climber is equal to the mass of the rock climber multiplied by her net acceleration, or F = ma = (50 kg) (5 m/s) = 250 N. The net force is equal to the vector sum of all of the forces acting on the rock climber. The two forces are tension (in the rope) and gravity, and they act in opposite directions, Fnet = Ft - Fg.. The force of gravity is Fg = mg = (50 kg)(10m/s) = 500 N directed downwards. The force of the tension in the rope is pointed up towards the helicopter, and is Ftorque = Fnet + Fgravity = 250 N + 500N= 750N
If all the resistors in the circuit pictured below have equal resistances, and the current flowing into resistor A is 4 amps. What is the current flowing into resistor F? A B ____________/\/\/\/\/___________/\/\/\/\________ I____________/\/\/\/\/\__________/\/\/\/\/\_______I I C D \ I < / E I F \> I___________________________/\/\/\/\/__________ / A. 2 A B. 4 A C. 8 A D. 16 A
C. 8 A this is Kirchoff's first rule; current flowing into a node must also flow out. Since the resistors have equal resistances, the current is the same in both parallel branches. Thus 4 amps flow into the node from both branches. Therefore 8 amps must flow out of the node.
All of the following expressions are equal to an Ohm EXCEPT: A. V x s/C B. W/A^2 C. A/V D. V^2 / W
C. A/V Choice A comes from V = iR, with I replaced by C/sec B comes from P= i^2R D comes from P = (V^2)/R
Consider a uniform magnetic field coming out of the page. There is a wire loop in the plane of the page. Which of the following would induce an electromotive force in the wire loop? I. increasing the magnitude of the magnetic field II. Rotating the wire loop to the right III. Moving the wire loop vertically out of the page. A. I and III B. I, II and III C. I and II D. III only
C. I and II Faradays' law states that a changing magnetic field will induce an electromotive force (EMF) in a wire. The goal of this problem is to figure out which of the options given produce a changing magnetic field with respect to the wire. Changing the magnitude of the magnetic field, option I, certainly does this. Eliminate answer choice D since it does not include option I. Moving the wire loop out of the page moves it along the same magnetic field lines. This does not change anything about the magnetic field felt by the wire and will not induce an electromotive force. Rotating the wire will change the magnetic field lines around the wire and induce an EMF.
In many harbors, old automobile tires are hung along the sides of wooden docks to cushion them from the impact of docking boats. The tires deform in accordance with Hooke's law. As a boat is brought to a stop by gently colliding with the tires, the rate of deceleration of the boat: A. is constant until the boat stops B. decreases until the boat stops C. increases until the boat stops D. increases and then decreases before the boat stops
C. increases until the boat stops. Since the tires follow Hooke's law, the force changes with the displacement of the tires. The greater the force, F = -k(delta x). The greater the force, the greater the acceleration, F=-k(delta x)=ma. Recall that the negative sign indicates direction, so compressing a spring results in a force in the opposite direction.
If the distance between a point charge and an infinitely large charged plate is increased by a factor of 2, the new force on the point charge will: A. decrease by a factor of 4 B. decrease by a factor of 2. C. remain the same D. increase by a factor of 2
C. remain the same The electric field above an infinitely large electric plate remains constant with distance. This can be visualized by imagining the electric field lines. The lines are perpendicular to the plate and have nowhere to spread. by bending in one direction or another, they would increase their distance from one line, only to decrease their distance from another line. Since the lines would remain at an equal distance from one another, the electric field would remain constant. If the electric field Is constant, the force must also be constant as given F= Eq
Objects A and B are placed on the spring as shown. Object A has twice as much mass as object B. If the spring is depressed and released, propelling the objects into the air, object A will: A. rise 1/4 as high as object B B. rise half as high as object B C. rise to the same height as object B D. rise twice as high as object B.
C. rise to the same height as object B A simple technique for solving this and many other physics problems is to "take the examples to extremes". Here the examples are reasonably close in mass. What if object A were one million times as massive as object B? In other words, imagine that object A is a piano and B is a dime. Now place them on a spring and propel the piano one inch in the air. Will the dime be propelled one million inches in the air at the same time? Of course not. Thus mass is not proportional to the height. Since all the answers are given as such, only C can be correct
Newton's law of universal gravitation states that any two objects attract each other with a force that is directly proportional to the product of their masses and indirectly proportional to the square of the distance between them. Thus, an object on the Earth's surface exerts a gravitational force on the Earth that is equal to that which the Earth exerts on it. Which of the following best describes the acceleration experienced by the earth? A. the earth is not accelerating towards the object B. the earth and the object are accelerating towards each other with the same acceleration C. the acceleration of the earth towards the object is small because the earth's mass is large D. the earth and the object are accelerating away from each other with the same acceleration
C. the acceleration of the earth towards the object is small because the earth's mass is large. The object exerts a gravitational force on the Earth equal in magnitude to the gravitational force exerted by the Earth on the object. However, acceleration is indirectly proportional to mass by Newton's second law. Thus the object with the larger mass will experience a smaller acceleration, and the object with the smaller mass will experience a larger acceleration. Since there is a net forceo n the earth and its mass is not zero, by Newton's second law the acceleration cannot be zero (though it may be very small); choice A is incorrect. Choices B and D are incorrect because although the force on the Earth and the object are equal in magnitude, their masses are not equal. Therefore they would not experience equal accelerations.
An airliner flies from Chicago to New York. Due to the shape of the earth, the airliner must follow a curved trajectory. How does the curved trajectory of the airliner affect its final displacement for this trip? A. the displacement is less than it would be if the airliner flew in a straight line to New York B. the displacement is greater than it would be if the airliner flew in a straight line to new York C. the displacement is the same as it would be if the airliner flew in a straight line to new York d. the final displacement of the airliner is zero
C. the displacement is the same as it would be if the airliner flew in a straight line to new York Because the start and end points of the trip do not change regardless of the path taken, the displacement for the trip does not change. Displacement is not the same as total distance. By following a curved trajectory, the plane will travel a farther distance
A piano creates the musical note when a metal wire stretched between two fixed ends is struck by a hammer, creating a standing wave. As the force with which the hammer strikes the string is increased, the amplitude of the string's motion is increased. Which of the following properties of the wave on the string will remain the same as the force of the hammer is increased? I. Frequency II. Wavelength III. Velocity A. I only B. I and II only C. II and III only D. I, II, and III
D. I, II, and III The velocity is a function of the properties of the string and is not affected by the force of the hammer. The wavelength of a standing wave is determined by the length of the string. The frequency depends on the wavelength and velocity of the wave, and is therefore also constant. If you hit the same piano key with increasing force, you will play the same note, you will just play it louder (larger amplitude)
Oxygen and carbon dioxide are exchanged at the interface between the alveolar wall and the pulmonary artery. Most of the carbon dioxide in the blood is carried in the form of bicarbonate ions: CO2 + H2O <---> HCO3- + H+ As carbon dioxide gas diffuses out of the blood and into the alveoli, the equilibrium shifts according to Le Chatelier's Principle. Which of the following best describes the partial pressure of CO2 in the pulmonary artery relative to that in the alveoli? A. The partial pressure of CO2 is lower in the pulmonary artery than in the alveoli. B. The partial pressure of CO2 is the same in the pulmonary artery and the alveoli. C. The partial pressure of CO2 is higher in the pulmonary artery than in the alveoli. D. the relative partial pressures of CO2 cannot be determined from the information given..
C. the partial pressure of CO2 is higher in the pulmonary artery than in the alveoli Don't be confused by the complicated question stem. The pulmonary artery is bringing blood from the body to the lungs where it will pick up oxygen and give off CO2. The CO2 will diffuse from an area of higher pressure to an area of lower pressure. If the CO2 is moving from the pulmonary artery to the alveoli, then the partial pressure of CO2 must be higher in the pulmonary artery than in the alveoli. Therefore, choice A is incorrect and C is the best answer. If the pressure were the same in the alveoli and the pulmonary artery, no CO2 exchange would occur, thus answer choice B is incorrect.
Which of the following is true regarding a tennis ball and a feather dropped from the same height? Assume that air resistance acts on both object. A. the tennis ball has more mass so it will fall faster B. the tennis ball has more surface area so it will fall faster C. the tennis ball has less surface area so it will fall faster D. the tennis ball has more weight so it falls faster.
C. the tennis ball has less surface area so it will fall faster The force of air resistance is dependent on the surface area, the shape, and the velocity of an object; the object's mass does not affect it. Surface area is directly proportional to air resistance. The feather has a larger surface area and experiences greater resistance or upward force. This results in smaller net force and smaller acceleration downward; choice B is incorrect. Acceleration due to gravity, g, is the same for all objects near the Earth's surface regardless of mass; choices A and D are incorrect
An automobile that was moving forward on a highway pulled over onto the exit ramp and slowed to a stop. While the automobile was slowing down, which of the following could be true? A. the velocity was positive and the acceleration was positive B. the velocity was negative and the acceleration was negative C. the velocity was positive and the acceleration was negative D. the velocity and acceleration had the same sign, either positive or negative.
C. the velocity was positive and the acceleration was negative Because the car is slowing down, the velocity and the acceleration are in opposite directions and must have opposite signs. The positive and negative refer to the direction are arbitrary as long as they are opposite. Only C meets this requirement
An object stands 4 cm in front of a converging lens. If the lens has a focal distance of 1 cm, where is the image formed? A. 0.75 cm in front of the lens B. 0.75 cm behind the lens C. 1 cm behind the lens D. 1.33 cm behind the lens
D. 1.33 cm behind the lens A converging lens forms a real, inverted image of an object outside its focal distance. Thus, if object distance is 4 cm and focal distance is 1 cm, the image formed must be real. Real images are images formed on the opposite side of the lens from the object. Therefore, if the object is in front of the lens, then the image must be behind the lens. choice A, which states that the image is formed in front of thel ens, can be eliminated. The thin lens equation states that 1/f = 1 / do + 1/di. Therefore, 1/di = 1/f - 1/do = 1/ (+1 cm) - 1/(+4cm) = 3/4 cm^-1 and di = 4/3 cm = 1.33 cm. choices B and C can be eliminated and choice D is the correct answer. Remember that, by convention, converging mirrors and lenses have positive focal distances and objects that are on the opposite side of a lens from an observer have positive object distances.
A 10 kg mass is in free fall with no air resistance. In order to slow the mass at a rate equal to the magnitude of g, an upward force must be applied with magnitude : A. 0 N B. 10 N C. 100 N D. 200 N
D. 200 N The downward force is mg=100 N. The first 100 N upward counters this to give a net force of 0 and thus a constant velocity. The question asks for a net force of mg = 100 N upwards. This requires adding another 100 N for a total of 200 N. Answer choice C is incorrect because it will balance the objects weight, give it a net force of 0 N, and thus an acceleration of 0.
object distance can be represented as what two letters
Do or P
If a selection of tubes differing in length and radius were subject to the same driving pressure, fluid in the tube with which combination of length, L, and radius, r, would flow at the greatest rate? A. L = 4 cm and r = 1 cm B. L = 2 cm and r = 1 cm C. L = 4 cm and r = 2 cm D. L = 2 cm and r = 2 cm
D. L = 2 cm and r = 2 cm Remember that flow rate, Q = ΔP/R, where P is pressure and R is resistance. Since all tubes would be subject to the same driving pressure, the tube with the least resistance would experience the greatest flow rate. Resistance, R, is directly proportional to L, and indirectly proportional to r^4. Therefore, the tube with the lowest L to r^4 ratio would experience the greatest flow rate. Choices A, B, C, and D are associated with ratios of 4, 2, 1/4, and 1/8, respectively. Therefore, choice D is the best choice. The fluid in the tube with a length of 2 cm and a cross=sectional radius of 2 cm
A lens is manufactured in such a way as to allow the object and the image to be at the same distance from the lens. If the lens is not flat, the only way this could be true is if the lens were: A. a diverging lens with the object at the focal distance B. a diverging lens with the object at twice the focal distance C. a converging lens with the object at the focal distance D. a converging lens with the object at twice the focal distance.
D. a converging lens with the object at twice the focal distance. no image is formed when an object is placed at the focal point of a lens. Therefore choices A and C can be eliminated. To decide between choices B and D, first assume that the lens is a diverging lens. Recall that diverging lenses form only virtual images, and, by convention, virtual images have negative image distances. Therefore, if the lens were a diverging lens and the object and image were at the same distance from the lens, di and do would be equal in magnitude but opposite in sign. If 1/f = 1/do + 1/di and di = -do, then 1 /f would equal 1/do + 1/(-do), which equals 0. If 1/f equaled zero, then f would equal infinity. Only flat mirror have a focal distance equal to infinity. Therefore, the lens cannot be a diverging lens and choice B can be eliminated. Choice D must be the correct answer. To confirm, recall that converging lenses form real images of objects placed outside their focal points. By convention, real images have positive image distances. Therefore, if the lens were a converging lens and the object were at twice the focal distance, then 1/f would equal 1/(2f) + 1/di, and di would equal 2f, as well. In othe words, if an object is palced at twice the focal distance of a converging lens, then the image formed will also be at twice the focal distance of the lens. Note that when the image is a real image, it will be on the opposite side of the lens from the object.
Electrophoresis is used to separate proteins according to their mass. Proteins are placed into a gel matrix and an electric field is applied. Which of the following will increase the speed at which the proteins move through the gel? A. increasing the size of the pores in the gel B. increasing the strength of the electric field C. Increasing the charge on the protein D. All of the above
D. all of the above All of these will change the magnitude of the force on the proteins and thus, by Newton's second law, change how fast they will accelerate from rest. The electric field, kq/r^2, and the charge are directly related to the electric force felt by the protein. Increasing the size of the pores will reduce the 'drag' caused by the gel and allow the proteins to move faster.
All of the following would increase the volume flow rate of a real fluid being pumped through a pipe EXCEPT: A. increasing the pressure difference between the ends of the pipe B. decreasing the fluid viscosity C. increasing the pipe radius D. increasing the length of the pipe.
D. because ΔP = QR, an increase in pressure difference (ΔP) or a decrease in resistance (R) increases flow (Q). Increasing the pipe radius decreases the resistance to flow. Increasing pipe length increases resistance to flow and decreases flow rate.
Compared to humans, bees perceive a slightly higher frequency of electromagnetic waves. Based on only this information, to which of the following flower colors is a bee more likely to be attracted? A. green B. red C. yellow D. blue
D. blue Of the given choices, blue light has the highest frequency. If the bees perceive higher frequencies, perhaps they are more likely to be attracted to blue. The mnemonic ROY G BIV will help you remember the order of frequencies of different colored light.
A large rock is tied to a rubber band and dropped straight down. As the rock falls, the rubber band gradually stretches, eventually bringing the rock to a stop. Which of the following energy transfers is taking place in this process? A. Kinetic to gravitational potential to elastic potential B. Kinetic to elastic potential to gravitational potential C. gravitational potential to elastic potential to kinetic D. gravitational potential to kinetic to elastic potential
D. gravitational to kinetic to elastic potential The rock starts out with gravitational potential energy. As it falls, it loses gravitational potential energy and gains kinetic energy. As the rubber band stretches, the rock slows to a stop and kinetic energy is transferred to the elastic potential energy of the rubber band; choice D reflects this transfer of energy
If a light on a dimmer switch is gradually turned down, it will generally show a red glow at the moment before it is turned off. This is because red light: A. moves more slowly through air than light of any other color B. moves more quickly through air than light of any other color C. has more energy than light of any other color D. has less energy than light of any other color
D. has less energy than light of any other color As the dimmer is turned down, less energy is provided to the light bulb filament until, finally, the only visible light produced is red. A similar effect is seen at night in a dying campfire, when only red coals remain. Remember that light of all colors moves through a given medium at the same speed, therefore, choices A and B are incorrect.
All of the following statements are true about a resonating string EXCEPT: A. a resonating string forms a standing wave. B. the wavelength created by a resonating string must coincide with one of its harmonics C. some spots on a resonating string will not move at all. D. if left alone, the amplitude of a wave on a resonating string will grow infinitely large.
D. if left alone, the amplitude of a wave on a resonating string will grow infinitely large. Amplitude of a standing wave is constant; D is false and thus is the correct answer. Nodes are the spots that will not move. Resonating strings form standing waves at wavelengths corresponding to their harmonics.
the symbol for any electric field is ____
E
hf =
E h is a proportionality constant known as plank's constant.
There are 3 forces acting on an object. Two of the forces are of equal magnitude. One of these forces pulls the object to the north and one pulls to the east. If the object undergoes no acceleration, then in which direction must the third force be pulling? A. northeast B. northwest C. southeast D. southwest
D. southwest The question stem states that "the object undergoes no acceleration" therefore, net force acting on the object must be equal to zero. If two forces of equal magnitude pull to the north and east, respectively, than the net force due to these two forces must be directed northeast. In order for net force to equal zero, the third force must be directed opposite to the vector sum of the first two. Therefore, it must be directed in the southwest direction.
A helium balloon will rise into the atmosphere until: A. the temperature of the helium inside the balloon is equal to the temperature of the air outside the balloon. B. The mass of the helium inside the balloon is equal to the mass of the air outside the balloon. C. the volume of the helium is equal to the volume of the air it displaces. D. the density of the helium in the balloon is equal to the density of the air surrounding the balloon
D. the density of the helium in the balloon is equal to the density of the air surrounding the balloon. The balloon rises because the buoyant force is greater than the weight. when these forces are equal, the balloon will stop rising. Thus the balloon stops rising when (density air)(V)(g) = (density helium)(V)(g). The volumes are always equal because the balloon is always fully submerged in the atmosphere. Another way to look at this problem is to see that the balloon is fully submerged in the fluid atmosphere. For the balloon to float, not rise or sink, use the floating equation: Fraction submerged = (density of object) / (density of fluid). The entire balloon is submerged, so the fraction submerged is equal to one. Choice A is incorrect because the temperature of the air and helium can be equal while their densities are not equal. Choice B is incorrect because the mall of the air outside the balloon is undefined. C is incorrect because the volumes of the helium and the displaced air are equal at all times.
The circuit shown below has 3 resistors connected in parallel to a circuit battery. If you add a 4th parallel resistor to the circuit, A. The voltage produced by the battery will be increased B. The voltage produced by the battery will be decreased C. the current produced by the battery will be decreased D. the power produced by the battery will be increased.
D. the power produced by the battery will be increased. Adding a resistor in parallel decreased the overall resistance, which will increase the current and the power. The voltage of the battery is not affected by changes in the circuit. Adding more resistors in parallel is equivalent to providing more branches through charge can flow
3 containers are filled with water to a depth of 1 meter. At the bottom of which container is the pressure the greatest? A B C _____ __________ _____________ / \ I I \ / /________\ I_________I \_______/ A. container A B. container B C. container C D. the pressure is the same at the bottom of all the containers.
D. the pressure is the same at the bottom of all the containers Pressure depends only on depth and density (P = pgh) , not the shape of the container
Doubling which of the following parameters will increase the volume flow rate, Q, between points A and B in a pipe by the greatest amount? Assume laminar flow. A. The distance between points A and B B. the difference in pressure between points A and B C. the viscosity of the fluid D. the radius of the pipe
D. the radius of the pipe Remember poiseuille's Law Q = ΔP (pi r ^4) _______ 8ηL The volume flow rate is directly proportional to r^4. Therefore, doubling the radius will increase Q by a factor of 16. Flow rate is inversely related to viscosity and length, so doubling these parameters will actually decrease the flow rate. doubling the difference in pressure between the two points will increase the volume flow rate, but only by a factor of 2.
Which of the following factors by itself will increase the frequency at which an observer hears a sound emanating from a source? A. the wind blows from the source to the observer B. the source and the observer move away from each other at the same speed. C. the source and the observer move in the same direction at the same speed D. the source moves away from the observer more slowly than the observer moves toward the source.
D. the source moves away from the observer more slowly than the observer moves toward the source The frequency will only increase when the distance between the source and observer is decreasing, as is the case in choice D. Choice B is the opposite situation. Wind has no effect on the velocity of the source and the observer, and does not affect the observed frequency. Objects moving at the same velocity do not get closer together.
The Earth moves around the sun at approximately 30 m/s. Is the Earth accelerating? A. no, because acceleration is a vector B. no, because the speed is constant C. yes, because the speed is not constant D. Yes, because the velocity is not constant
D. yes, because the velocity is not constant Acceleration is the rate of change of velocity. Since velocity is a vector, it specifies magnitude and direction. Even if speed stays constant, the direction of the Earth's motion is constantly changing. Therefore, the Earth is accelerating; choices B and C are incorrect. choice A makes a true statement, but does not answer the question
____________ states that the objects force is directly proportional to the amount of deformation, or more precisely, the change in position (delta x).
Hooke's law
compressing or stretching an object creates another type of force, which follows _______________
Hooke's law
The instantaneous power due to a force is given by which formula?
P = Fv cosθ θ = angle between F and v F = force in the direction of the velocity
For a fluid at rest with uniform density in a sealed container, pressure P is given by what formula
P = pgy p = density of fluid g is gravitational constant y is the depth of the fluid
in any fluid open to the atmosphere, the pressure can be found by which formula
P = pgy + P(atmosphere)
________ law is commonly used to predict the flow rate of real fluids, including blood in the circulatory system.
Poiseuille's Law
1 / f =
T
A cell at rest has a potential of -70 mV across it's membrane. Assume the diameter of the cell is 20 micrometers. The cell membrane has a capacitance of 1 microF / cm ^2 Elementary charge = 1.6 x 10^-19 C. How many potassium ions in the cell are needed to charge the cell membrane? A. 220 ions B. 560 ions C. 5.6 x 10^4 ions 2.2 x 10^15 ion
The surface area of the cell is, SA = πr^2 = π (10 x 10^-6 m)^2 = 3.14 x 10^-8 cm^2. The capacitance of cell membrane is, (1 μF/ cm^2)( 3.14 x 10^-8 cm^2) = 3.14 x 10^-8 μF = 3.14 x 10^-14 The charge that a capacitor can hold at a certain voltage is given by, Q=CV = (3.14 x 10^-14 F)(70 x 10^-3 V) = 220 x 10^-17 Every ion of potassium will have a charge of +e, (2.2 x 10^-15 C ) / (1.6 x 10^-19 C ) / potassium ion = 1.4 x 10 ^ -4 ions
a particle moving forward in a straight line slows down at a constant rate from 50 m/s to 25 m/s in 2 seconds. What is the acceleration of the particle? A. -12.5 m/s^2 B. -25 m/s^2 C. + 12.5 m/s^2 D. + 25 m/s^s
This is a plug-and-chug problem using the formula v=v0 + at, which results in 25 m/s = 50 m/s + a(2s). Thus a=-12.5 m/s^2. If it had taken only one second to slow from 50 to 25 m/s, the acceleration would have been -25 m/s^2, but it took two seconds, so acceleration is smaller in magnitude. The answer is negative because the particle is slowing down, eliminating C and D.
K (q1) ______ = r
V (be careful not to mistake for r^2 which would make it E)
1/2 (V + V0) =
V average
________ is the potential for work by an electric field in moving any charge from one point to another
Voltage
_______ of a wave represented by sine function can be measured as the distance between the x-axis and either the top of a crest or the bottom of a trough
amplitude
an ________ is created by two opposite charges with equal magnitude
an electric dipole
a ____________ is a vector whose magnitude is the charge q on one of the charges multiplied by the distance d between the charges. In physics, this vector points in the opposite direction to the electric field, from the negative charge to the positive charge
an electric dipole moment
a ____________ is a representation of an object derived from the light reflected from the object
an image
the angle at which a wave strikes an interface is called the ___________
angle of incidence
___________ arise when light of higher frequencies focuses closer to a lens than does light of lower frequencies
chromatic aberrations
