mcat physics memorize

Right hand rule

(A magnetic field is measured at point A in Figure 1. Which of the following is true?) The induced magnetic field points into the page bc electrons flow from left to right and current flows opposite of e-, so it flows from right to left. Right thumb points to left and fingers curled around wire means magnetic fields point into page (NS 8.4)

pobj/pfluid = submerged or above? Assume that the density of Ball 1 is 8.0 × 102 kg/m3. Ignoring the atmospheric pressure, what fraction of Ball 1 is above the surface of the water? 4/5, 3/4,1/4, 1/5

(D1/ρ)V = (800/1000)V = 0.8V. This tells us that 0.8V is below the surface, thus V - 0.8V = 0.2V must be above the surface. The fraction of ball 1 above the surface is thus 2/10 = 1/5.

log(.001)

-3

Log3 =

.48

What is 2/3

.66

x/11 =

.x9x9x9x9 .0909090909 .1818181818181818 .272727272727

x/9=

.xxxxx 1/9 = .11111 2/9 = .22222 3/9 = .33333

cos90

0

sin(0)

0

log 2 =

0.3

5/8

0.625, 62.5%

cos(0)

1

sin90

1

1 ev = ? J

1 eV = 1.6 x 10^-19 J

mmHg to torr

1 mmHg = 1 torr

√2 =

1.4

√3 =

1.7 (3/17 St. Patty's)

cos60

1/2

sin30

1/2

Suppose a certain far-sighted person can see objects clearly no closer than 300 cm away. What is the minimum distance from a plane mirror such a person must be to see his reflection clearly? 150cm 300cm

1/o + 1/i = 1/f, 1/o = - 1/i The object distance and the image distance are equal. So, if the far sighted person can only see clearly no closer than 300 cm, the person needs to be standing 150 cm in front of the mirror because the image is produced 150 cm behind the mirror.

1atm = ? pascals

101,000 pascals

4/(4/3) =

12/4 = 3

How many degrees is complete destructive interference?

180 degrees

1800/4.5 =

1800(9/2) = 2/9 x 1800 = (2 x 1800)/9 = 400

A single 4uf capacitor is added in series with a set of parallel capacitors each with 2uF. What is the ratio of the new capacitance to the orig equivalent capacitance?

1:2 Cparallel = C+C+C 2uF +2uF = 4uF 1C = 1/4uF + 1/4uF = 1/2uF Ceq = 2uF

8/3=

24/9 = 24/10 = 2.4

25^2

625

What is 16 x 4

64

7/5=

70/50 = 140/100 = 1.4

P1 - P2 =

8nlQ/pir^4

Farenheit

9/5C+32

How many degrees is constructive interference or no interference?

90 degrees

Which experiment can be used to investigate the transcriptional regulation of the Cdkn1a protein? (which method is transcriptional) A. Assessing Cdkn1a mRNA levels by RT-PCR B. Assessing Cdkn1a mRNA levels by Southern blotting C. Assessing Cdkn1a protein levels by quantitative PCR D. Assessing Cdkn1a protein levels by Western blotting

A. As the question is focused on the transcriptional regulation, it is logical to assess the mRNA levels as opposed to protein levels. RT-PCR is a molecular technique that measures mRNA levels of specific protein. Western blot is translational and not transcriptional

The inner mitochondrial membrane has a thickness of 5 nm and an average membrane potential of 150 mV. What is the magnitude of the electric field across the mitochondrial membrane in these cells? E=? A. 3 x 10^-2 V/m B. 3 x 10^4 V/m C. 3 x 10^7 V/m D. 3 x 10^10 V/m

C. 3 x 10^7 V/m E = V/d E = (0.15 V) / (5 x 10-9 m) = 3 x 107 V/m.

When a downward force is applied at a point 0.60 m to the left of a fulcrum, equilibrium is obtained by placing a mass of 10-7 kg at a point 0.40 m to the right of the fulcrum. What is the magnitude of the downward force?

Classic problem of torque. F1r1 = F2r2. F1r1 = m2a2r2 , F1 = m2a2r2/r1 = 10*10^-7*10*0.4/0.6 = 40*10^-7/6 = 6.5*10^-7

A 15.0-eV photon collides with and ionizes a hydrogen atom. If the atom was originally in the ground state (ionization potential =13.6 eV), what is the kinetic energy of the ejected electron? 1.4ev 13.6ev 15ev 28.6ev

Conservation of energy requires that the 15.0 eV photon energy first provides the ionization energy to unbind the electron, and then allows any excess energy to become the electron's kinetic energy. The kinetic energy in this case is 15.0 eV - 13.6 eV = 1.4 eV.

change in potential energy

Delta U = UB - UA A point particle has a charge of -8uC. It moves from point A with electric potential VA=+200V to point B, with electric potential VB = +600V. What is the change in potential energy as a result of this movement? U = qVb - qVa U = (-8uC)(600J/C) - (-8x10^6C)(200J/C) =-.0032J Change in PE due to mvt of point particle = -.0032J

If the magnitude of a positive charge is tripled, what is the ratio of the original value of the electric field at a point to the new value of the electric field at that same point? (what is the relationship btw q and E) 1:2 1:3 1:6 1:9

E = kq/r^2 1:3

Coloumb's Law

F = kq1q2/r^2

Electric Field force

F=qE What is the magnitude and direction of force exerted on a 3.5 uC charge by a 250 N/C electric field points due east?

Is ultrasound frequency higher or lower than human hearing span? The typical range of human hearing spans from 20 Hz to 20,000 Hz, and the speed of sound in air is approximately 340 m/s. With this information in mind, an ultrasound signal:

Higher, so it is higher than 20,000 hz and has a wavelength lower than .017m 340 m/s = λ(20000 Hz) 3.4 x 102 m/s = λ(2 x 104 Hz) λ =(3.4 x 102 m/s) / (2 x 104 Hz) λ =1.7 x 10-2 m = 0.017 m

I = P/?

I = P/A A woman is standing two meters away from a speaker. The speaker is turned up to 11 on its dial, and the power of the sound hitting her tympanic membrane increases 100-fold. How far would the woman need to move to reduce the sound back to its original decibel level? I = P/A A= 4pir^2 dB = 10log (I/Io) In order to increase the area 100-fold, the radius, r, must increase by a factor of 10 (102 = 100). Thus, if the woman originally stands two meters away then to maintain the same decibel level, she needs to stand 2 x 10 = 20 m away from the speaker. Standing 2 m away, the woman must move 18 m.

I= P? If the red LED used in this experiment was designed to operate at 30 mW and there was a voltage drop of 3.2 V when the LED was lit, what was the current flowing in the circuit? A. 9.4 x 10-3 amps B. 1.0 x 10-1 amps C. 9.4 x 100 amps D. 1.1 x 102 amps

I = P/V A. 9.4 x 10-3 amps (3.0 x 10-2 V-amp) / (3.2 V) ~ 1 x 10-2 amps

Shortcut for di image in optics formula

I = of/o-f

The hydrotrope sodium benzoate is formed by the reaction of NaOH and benzoic acid. In an aqueous solution, this hydrotrope is: weakly acidic strongly acidic weakly basic strongly basic

In this case in particular, because benzoic acid is a weak acid, it relatively firmly holds on to its acidic proton. So after the benzoic acid has been deprotonated, the resulting benzoate grabs the few protons from the dissociated water, leaving only hydroxides. By LeChatelier's Principle, more water dissociates, resulting in more hydroxides and protons. Benzoates take the protons, which leads to more benzoic acid and more dissociation of water. The process continues until both water's and benzoic acid's equilibrium constants are reached. A moderate excess of hydroxides, beyond the number of protons, results.

Newton units

Kg . m/s^2

How will W change if the angle of the ramp to the horizontal is increased? W will decrease bc normal force to surface of ramp will decrease, w will not change

Kinetic friction F acts up the ramp and d is down the ramp, so θ= 180°, hence W = −Fd. The kinetic friction force F is the product of the normal force N that the ramp exerts on the mass and the coefficient of kinetic friction μkh. Thus W = − μkhNd. Increasing the tilt of the ramp has no effect on d or μkh, but it does decrease normal force N. For a very steep ramp, the mass is nearly in free fall and pushes down on the ramp very little, hence N is small.

open ended length sound

L = nlambda/2

close ended length sound

L = nlambda/4

M = what relationship with image?

M = (hi/ho) = (di/do) What is the height of the image of an apple (h = 12 cm) sitting 2 meters away that is projected onto your retina if the focal length of the retina is 20 millimeters? .12 cm M = 12cm/h = -200cm/2cm = .12cm

If the magnitude of a positive charge is tripled, what is the ratio of the original value of the electric field at a point to the new value of the electric field at that same point? 1:2 1:3 1:6 1:9

N. E = kq/r^2

pascal units

N/m^2

Power formula in relation to force

Power = FxD/t

Convex lens 2f < image < f (converging)

Real and Enlarged

Convex lens image > 2f (converging)

Real and reduced

velocity in relation to mass and KE

Square root of (2KE/m)

Torque equation

T = rFsin(theta)

An object that is totally immersed in benzene (specific gravity = 0.7) is subject to a buoyancy force of 5 N. When the same object is totally immersed in an unknown liquid, the buoyancy force is 12 N. What is the approximate specific gravity of the unknown liquid? .3 .9 1.7 2.3

The buoyant force on an immersed object is the product of: (density of the liquid) × (volume of the object) × (acceleration of gravity). Forming the ratio of buoyant forces in the two cases gives: 12/5 = (density of the unknown liquid)/(density of benzene, 0.7). Solving for the specific gravity of the unknown liquid, which is the ratio of its density to that of water, gives (12/5) × 0.7 = 1.7. pvgunknown/pvgknnown =pkunknown/pknownFb density*g*V, 5N = density*0.7, density = 50/7, Fb/density = g, 12N*7/50 = 84/50 = 168/50 = 1.7

A charged particle with a mass of m and a charge of q is injected midway between the plates of a capacitor that has a uniform electric field of E. What is the acceleration of this particle due to the electric field?

The force on the charge is qE and force is also ma. Setting qE = ma and solving for acceleration a yields a = Eq/m

Which technique separates proteins independently of their charge? A. Native PAGE B. Gel filtration chromatography C. Ion exchange chromatography D. Isoelectric focusing

The solution is B. Native PAGE is used to separate molecules based on their electrophoretic mobility, relying on length, conformation, and charge. Gel filtration chromatography separates protein only on the basis of their size.

One company sells a defibrillator for home use that uses a 9-volt DC battery. The battery is rated at 4.2 A•hr (amp•hour). Roughly how much charge can the battery deliver? A. 4.2 C B. 38 C C. 15,000 C D. 136,000 C

The solution is C. This is the charge delivered in one second based on the calculation 4.2 A × 1 s = 4.2 C. The magnitude is computed as an approximation of 4.2 × 9 = 37.8 ≈ 38. However, multiplying the corresponding units V × A•hr yields J, not C. The definition of current is flow of charge per unit time. Thus, charge equals current multiplied by time, hence 4.2 A × 1 hr = 4.2 A × 3600 s = 15,120 C ≈ 15,000 C.

Energy stored by capacitors (A capacitor is connected to a battery with a voltage of 5V. Its capacitance is 2 uF. What is the energy storied in the capacitor?

U = 1/2QV = 1/2CV^2 = 1/2Q^2/C U = 1/2CV^2 = 1/2 (2 *10^(-6)F) * (5V)^2 U = 25*10^-6 J

Which of the following will occur when the magnet used in the flowmeter discussed in the passage is replaced with a stronger magnet? voltage will increase, blood will flow faster, electric field will decrease, electric field will reverse polarity

V = F(electric)d/q Fm = q v B^. The electric force must also increase to achieve equilibrium. This implies a larger electric field in the artery and a larger voltage across the artery.

Convex lens f. Pos image < f (converging)

Virtual and Enlarged

concave lens f. Neg (diverging)

Virtual at all distances and reduced

if given mass, change in velocity, how can you find work done? a seatbelt holds a 70kg crash test dummy in the car seat during a collision that slows the car from 90km/hr to 0 km/hr/ What is approx magnitude of work done by seat belt on crash test dummy? a. 2000j b. 20000j c. 40000j d. 300000j

W = 1/2mv^2 v = 90000m/hr x 1hr/3600s = 25 =-1/2(70kg)(25^2) = 1/2(70kg)(625m^3/s^2) = -21000 kg x m^2/s^2 = -20000J

If given distance, acceleration, mass, how would you find work? Assuming an average displacement of 0.25 m per hit and that the human head weighs 5 kg, approximately how much work was done on athlete 5's head over the course of the season? acceleration = 32g and there were 1850 hits total

W = F x d = m x a x d = 5kg x (32 x 10) x .25 = 400J x 1850 = 1740 x 10^3 J

A 2kg block slide down a 3m long frictionless 30 degree incline. How much work does gravity do on block? A. 30J B. 40J C. 50J D. 60J

W = mgdsintheta 2kg x 3m x 10 x sin30 = 30J

How will W change if the initial speed of the box at Point A is increased by a factor of 2?

W will not change bc w = fdcostheta

How many degrees is complete constructive interference?

Zero degrees

how to find how far an object goes to reach top of trajectory? an obj projected upward at 30 angle with horizontal with initial speed of 60m/s. How long will it take to reach top of trajectory?

a = v/t -> t = v/a 60sin30/10 = 3

if given a speed vs time graph, and a dashed line as a slope what value does it represent? a. acceleration b. displacement c. kinetic energy d. work done

a. acceleration bc speed/time = acceleration

does paramagnetic mean that electron spins align parallel to applied magnetic field or they repel magnetic field lines?

align parallel to applied magnetic field

A ray of light in air strikes the flat surface of a liquid, resulting in a reflected ray and a refracted ray. If the angle of reflection is known, what additional information is needed in order to determine the relative refractive index of the liquid compared to air? angle of incidence angle of refraction refractive index o air wavelength of light

angle of refraction Snell's law. n1sinθ1 = n2sinθ2 so n2/n1 = sinθ1/sinθ2, and since θ1 can be calculated from the angle of reflection, you only need θ2 the angle of refraction to determine n2/n1 (B)

An unknown solid weighs 31.6 N. When submerged in water, its apparent weight is 19.8 N. What is the specific gravity of the unknown sample? 2.96 2.68 2.02 1.68

b. The buoyant force on the solid is the difference between its weight (31.6 N) and its apparent weight in water (19.8 N). This force equals the weight of the water displaced, which, in turn, equals the product of the volume of the solid and the density of water. The specific gravity of the solid, i.e., the ratio of its weight to the weight of an equal volume of water, is then: 31.6/(31.6 -19.8) = 2.68.

Sound waves reaching the ultrasonic transducer propagate through brain tissue via which of the following mechanisms? collision of particles and/or vibration of particles parallel to direction of wave motion in tissue

both

closed vs isolated system

closed exchanges heat but not matter isolated doesn't exchange heat or matter

what is relationship btw conductivity and resistivity? if new resistor had 75% lower conductivity, then I would:

conductivity = 1/resistivity decrease by factor of 4 bc conductivity is now 1/4 the orig value, so resistivity must've increased by 4 and - = v/r

How long will it take a runner, starting from rest and accelerating uniformly at 1.5 m/s2, to travel 3.0 m? 2^1/2sec 1.5sec 2sec 3sec

d = (1/2)a • t2. To solve for the time it takes the runner to use t = (2d/a)1/2 = (2 • 3/1.5)1/2 = 2 s.

After a block began to slide, how did its speed vary with time? (Note: Assume that the tension and kinetic friction forces on the block were constant in magnitude.) a. it was constant b. it increased exponentially with time c. it was first constant, then increased linearly with time d. it increased linearly with time

d. Gravity. The block on the right pulls with whatever its weight is. As long as that force is greater than the frictional force between the left block and the board, we'll accelerate. The coefficient of kinetic friction is always lower than that of static friction. Therefore there is a net accelerating force on the block once it starts to slide. A constant force on a mass produces a constant acceleration (Newton's second law). Thus, the velocity of the block increases linearly with time. https://www.youtube.com/watch?v=t67hldWANqc

Focal length & radius of curvature

f = R/2

kinetic friction formula what is the the acceleration vector of the box as it moves from Point B to Point C (down a ramp)? -um or um

fk = ukN = umg bc N = mg ma = - umg a = -ug but it is neg bc friction in opp direction of the box

wavelength distance between nodes

half a wavelength

in a parallel circuit, what happens to equivalent resistance when you take a resistor away?

it increases bc R = 1/R+1/R+1/R means that R/1+1 will have a larger denominator and hence lower R.

if you are given a velocity vs time chart, how do you find distance travelled?

it is the area under the chart.

fluid density units

kg/m^3

destructive wavelengths differ by

lambda/2

log(0.33) = log(1/3) = log(1.5) = log(3/2) = log(5) = log(10/2) =

log(1) - log(3) = 0 - 0.48 = -0.48 log(3) - log(2) = 0.48 - 0.3 = 0.18 log(10) - log(2) = 1 - 0.3 = 0.7

momentum formula two moving bodies a and b are unequal mass. they meet headon and come to rest as result of perfectly inelastic collision. Prior to collision, body a was traveling at speed 10 times that of body b. which of the following represents the ratio of mass of a to mass of b?

mAvA = mBvB mB/mA = vA/vB vA/vB = 10 mB/mA = 10 mA/mB = 1/10

momentum =

mass x velocity

Is Ff in an inclinced plane mgsintheta or mgcostheta

mgsinthetea

Diverging lens is positive or negative focal length?

negative

Myopia is solved by positive or negative focal length?

negative

is perceived frequency for an obj that is moving different from another obj that is moving further away if it has a greater distance from the observer?

no bc

Sound of a known frequency, wavelength, intensity, and speed travels through air and bounces off an imperfect reflector which is moving toward the source. Which of the following properties of the sound remains the same before and after reflection? speed, frequency, wavelength, intensity

speed bc speed of sound depends on medium while frequency of sound is constant in medium but not necessarily in reflector

A 0.5-kg uniform meter stick is suspended by a single string at the 30-cm mark. A 0.2-kg mass hangs at the 80 cm mark. What mass hung at the 10-cm mark will produce equilibrium? .3kg .5kg .7kg 1kg

torque left of the suspension will be mg(20 cm). There are two torques right of the suspension, the hanging mass torque (0.2 kg)g(50 cm) and the weight of the meter stick's torque (0.5 kg)g(20 cm), where 20 cm represents the distance from the suspension to the center of mass of the meter stick. Thus, the net right torque is (0.2 kg)g(50 cm) + (0.5 kg)g(20 cm). Equating the left and right net torques yields m = 1 kg

v = ___+ ___

v = v0 + at

v^2 =

v^2 = v0^2+2a(x-x0)

aamc for object lengths larger than focal lengths in diverging lenses the image is?

virtual and reduced

how to find distance from horizontal projection? object projected upward at 60degrees angle with horizontal and initial speed of 30m/s. How far will it travel horizontally in its first three seconds of flight?

x = vcos(t) =30m/s cos60 = 45

x =___ + ___ +___

x =x0 + v0t + 1/2at^2

cos45

√2/2

sin45

√2/2

cos30

√3/2

sin60

√3/2