Physics Study Cards
A force of 88 N pushes down on the movable piston of a closed cylinder containing a gas. The piston's area is 0.4 m2. What is the pressure produced in the gas?
88N / .4m2 = 220 Pa
Two forces are applied to a merry-go-round with a radius of 4.2 m as shown in the following diagram. One force has a magnitude of 90 N and the other a magnitude of 40 N. Take the torque caused by the 90-N force to be positive. The torque about the axle of the merry-go-round due to the 90-N force is ____N·m. The torque about the axle of the merry-go-round due to the 40-N force is _____N·m. The net torque acting on the merry-go-round is _____N·m
90 N(4.2 m) = 378 N⋅m −40 N(4.2 m) =-168 N⋅m [Negative sign indicates the direction of the resulting torque] (378 N⋅m)+(-168 N⋅m) = 210 N⋅m
The readings of a given temperature on the Celsius and Fahrenheit scales
Could be equal, are equal at -40
What is the physical principle that best explains the macaroni rising and falling in a pot of boiling water?
convection current
For an ideal gas, all of the internal energy of the gas is ___energy
kinetic
The internal energy of a system is defined as the sum of the ___ and ___ energies at the microscopic level.
kinetic potential
The amount of heat added per unit mass to produce a phase change is called the ___ heat
latent
A 0.73-kg block of wood is floating in water. Determine the magnitude of the buoyant force acting on the block (given: g = 9.8 m/s2).
(.73) x (9.8) = 7.2
A student, sitting on a stool, holds masses in each hand. When his arms are extended, the total rotational inertia of the system is 5.6 kg·m^2. When he pulls his arms in close to his body, he reduces the total rotational inertia to 1.4 kg·m^2. When he is rotating with his hands held close to his body, his rotational velocity is 22 RPM. If there are no external torques, calculate the new rotational velocity of the system when he extends his arms.
(1.4 kg⋅m^2×22 rpm)/5.6 kg⋅m^2 = 5.5 RPM
A block of wood of uniform density floats so that exactly one quarter of its volume is underwater. The density of water is 1000 kg/m3. What is the density of the block?
(1000) x (.25) = 250
A rock with a volume of 1.5 m3 is fully submerged in water having a density of 1000 kg/m3. What is the buoyant force acting on the rock (given: g = 9.8 m/s2)?
(1000) x (1.5) = 1500 x 9.8 = 14700 (which is 14.7 x 10^3)
With the temperature held constant, the piston of a cylinder containing a gas is pulled out so that the volume of the gas increases from 0.2 m3 to 0.5 m3. If the initial pressure of the gas was 106 kPa, what is the final pressure?
(106) x (0.2 / 0.5) = 42.4
With the temperature held constant, the pressure of a gas in a cylinder with a movable piston is increased from 16 kPa to 40 kPa. The initial volume of the gas in the cylinder is 0.75 m3. What is the final volume of the gas after the pressure is increased?
(16 x .75) / 40 = 0.3
The rotational velocity of a merry-go-round increases at a constant rate from 2.5 rad/s to 18.6 rad/s in a time of 12.5 s. What is the rotational acceleration of the merry-go-round? The rotational acceleration of the merry-go-round is____
(18.6 rad/s−2.5 rad/s) / 12.5 s = 1.288
A weight of 24 N is located 12 cm from the fulcrum on the beam of a simple balance. Determine the weight that should be placed at a point 5 cm from the fulcrum on the opposite side in order to balance the system. The weight that should be placed at a point 5 cm from the fulcrum on the opposite side is____
(24 N)⋅12 cm/5 cm = 57.6 N
The rotational velocity of a spinning disk decreases from 19 rev/s to 3 rev/s in a time of 15 s. What is the rotational acceleration of the disk? Take the initial and final directions of rotation to be positive. The rotational acceleration of the disk is ____ rev/s^2
(3 rev/s − 19 rev/s) /15 s = -1.0667 rev/s^2
A stream moving with a speed of 5.7 m/s reaches a point where the cross-sectional area of the stream decreases to one half of the original area. What is the speed of the water in this narrowed portion of the stream?
(5.7) x (2) = 11.4
The pressure of a gas contained in a cylinder with a movable piston is 526 Pa (526 N/m2). The area of the piston is 0.3 m2. What is the magnitude of the force exerted on the piston by the gas?
(526)(0.3) = 157.8
A certain boat displaces a volume of 9.2 m3 of water. (The density of water is 1000 kg/m3.) The mass of the water displaced by the boat is ____ kg. The buoyant force acting on the boat is ___ kN.
(9.2) x (1000) = 9200 (1000) x (9.8) x (9.2) = 90160 / 1000 = 90.16 kN
A disk is initially spinning with a rotational velocity of 16 rad/sec. The disk's rotational velocity is decreased to 10 rad/rec over a 2 second interval. The rotational acceleration during that 2 second time interval is ____ rad/sec
-3 10-16/2 =-3 rad/sec
In order for an object to be in equilibrium, the net torque on it must be ___N m.
0 (zero)
A merry-go-round starts from rest and accelerates at a constant rate of 0.8 rev/s^2. What is its rotational velocity after 6 s?______ How many revolutions does the merry-go-round make in 6 s____?
0+(0.8 rev/s^2)(6 s) = 4.8 rev/s 0+1/2(0.8 rev/s^2)(6 s)^2 = 14.4 rev
A bicycle wheel is rotationally accelerated at a constant rate of 2 rev/s^2. The wheel's rotational velocity is ___rev/s? The number of revolutions made by the wheel is_____
0+(2 rev/s^2×5 s) = 10 rev/s 0+1/2(2 rev/s^2×(5 s)^2)= 25 rev
The temp of a 50g sample of aluminum is raised for 20 degrees C to 90 degrees C when 770 cal of heat are added. The specific heat capacity of the aluminum is _____cal/g degrees C
0.22 770 cal / (50g x 70 degrees C) = 0.22
A mass of 0.7 kg is located at the end of a very light and rigid rod 60 cm in length. The rod is rotating about an axis at its opposite end with a rotational velocity of 12 rad/s. What is the rotational inertia of the system? What is the angular momentum of the system?
0.7 kg×(0.6 m)^2= 0.252 kg⋅m^2 0.252 kg⋅m^2×(12 rad/s) = 3.024 kg⋅m^2/s
Two 0.8-kg masses are located at either end of a 1.4-m long, very light and rigid rod. What is the rotational inertia of the system about an axis through the center of the rod?
0.8 kg×(0.7 m)^2=0.392 kg⋅m^2 Because there are two identical masses located the same distance away from that axis, the total rotational inertia of the system is 2(0.392)= 0.784 kg⋅m^2
Water emerges from a faucet at a speed of 1.5 m/s. After falling a short distance, its speed increases to 4.4 m/s as a result of the gravitational acceleration. By what number should the original cross-sectional area of the stream be multiplied to find the area at the lower position?
1.5 / 4.4 = 0.34
A uniform disk with a mass of 7 kg and a radius of 1 m is rotating with a rotational velocity of 15 rad/s. What is the rotational inertia of the disk? What is the angular momentum of the disk?
1/2 (7 kg×(1 m)^2) = 3.5 kg⋅m^2 3.5 kg⋅m^2×(15 rad/s) = 52.5 kg⋅m^2/s
On the Celsius scale, the difference between the freezing and boiling points of water is ___ degrees
100
When food packaging list the calorie count for a given item, it is actually referring to the food calories. That means that for every "calorie" you get from the food you eat, there are ___heat calories
1000
A net torque of 120 N·m is applied to a disk with a rotational inertia of 11.0 kg·m^2. What is the rotational acceleration of the disk?
120 N⋅m/11.0 kg⋅m^2 =10.9091 rad/s^2
A wheel displaces 10 revolutions over a 5 second interval. The rotational velocity during that 5 second interval time was ____revs/sec
2 10 revs/5 secs = 2 revs/sec
A force of 20 N is applied at the end of a wrench handle that is 24 cm long. The force is applied in a direction perpendicular to the handle. The torque applied to the nut by the wrench is_____N·m. Calculate the torque if the force is applied halfway up the handle instead of at the end._____
20 N⋅(24 cm×1 m/100 cm)= 4.8 N⋅m 20 N⋅(24 cm×1/2×1 m/100 cm)= 2.4 N⋅m
Which numbers represent the freezing point of water?
273 K 0 degrees C 32 degrees F
A 340-lb woman puts all of her weight on one heel of her high-heeled shoes. The heel has an area of 0.25 in2. What is the pressure exerted by her heel on the ground in pounds per square inch (psi)?
340 / .25 = 1360
A mixture consists of 50g of ice and 100g of liquid water both at 0 degrees C. The amount of heat that must be added to melt all of the ice is ___cal. The heat of fusion of ice is 80 cal/g and the specific heat capacity of water is 1.0 cal/g C
4000 50g x 80 cal/g
How much heat do you need to take from a 1g sample of boiling water to lower its temp to 0 degrees C?
418 J or 100 cal
In a hydraulic system, a force of 576 N is exerted on a piston with an area of 0.002 m2. The load-bearing piston in the system has an area of 0.3 m2. The pressure in the hydraulic fluid is _____ What is the magnitude of the force exerted on the load-bearing piston by the hydraulic fluid?
576 / 0.002 = 288000 / 1000 = 288kPa 288 x 0.3 = 86.4 = 8.64 x 10^4 N
A weight of 60 N is located at a distance of 8 cm from the fulcrum of a simple balance beam. At what distance from the fulcrum should a weight of 25 N be placed on the opposite side in order to balance the system? The required distance from the fulcrum to balance the system is______
60 N⋅ 8 cm/25 N = 19.2 cm
A torque of 62 N·m producing a counterclockwise rotation is applied to a wheel about its axle. A frictional torque of 14 N·m acts at the axle. What is the net torque about the axle of the wheel? If the wheel is observed to accelerate at the rate of 6 rad/s2 under the influence of these torques, what is the rotational inertia of the wheel?
62 N⋅m+(−14 N⋅m) = 48 N⋅m 48 N⋅m/6 rad/s^2 = 8 kg⋅m^2
The load-bearing piston in a certain hydraulic system has an area 86 times as large as the input piston. If the larger piston supports a load of 6320 N, how large a force must be applied to the input piston?
6320 / 86 = 73.5
A column of water in a vertical pipe has a cross-sectional area of 0.32 m2 and a weight of 725 N. What is the increase in pressure (in Pa) from the top to the bottom of the pipe?
725 / 0.32 = 2265.6
An airplane wing with an average cross-sectional area of 8 m2 experiences a lift force of 79000 N. What is the difference in air pressure, on an average, between the bottom and the top of the wing?
79000 / 8 = 9875
A wheel with a rotational inertia of 8.3 kg·m2 accelerates at a rate of 3.8 rad/s2. What net torque is needed to produce this acceleration?
8.3 kg⋅m^2×(3.8 rad/s^2) = 31.54 N⋅m
The shower curtain moves toward the water when water is turned on. What is the underlying physical principle
Bernoulli's Principle
Rank of high to low the following materials based on their specific heat capacities: a)The temp of 1 kg of this material can be raised 10 degrees C by 500 calories amount of heat b)The temp of 1 kg of this material can be raised 10 degrees C by 1000 calories amount of heat c)The temp of 1 kg of this material can be raised 10 degrees C by 2000 calories amount of heat
C is highest B is next A is lowest
A figure skater is spinning with her arms extended. She now pulls her arms close to her body. What happens?
Her rotational inertia decrease
If heat transfer form object A to object B, this means that object A is ___ than object B
Hotter
The primary mode of energy transfer when you use a heating blanker to get warm is____
conduction
In the equation of state (PV = NkT), T is the temp and should be expressed in ___
Kelvin
A helium filled balloon rises in air because it is:
Less dense and bigger
The net force acting on a free, submerged object will be the difference between the weight of the object and buoyancy force acting on the object. Match the pairs together: Sink Float up Remain at the same level
Sink=the density of the object is greater than the density of the water. Float up=the density of the object is greater than the density of water. Remain the same level=the density of the object is the same as the density of the water.
The equation of state for the same amount of an ideal gas at two different temps T1 and T2 could be written as:
T1 / T2 = (P1 x V1) / (P2 x V2) (P1 x V1) / T1 = (P2 xV2) / T2
Thermal conductivity depends on
The difference in temp and the type of material
Why does a metal door know feel coder than a wooden door if they are both at the same temp?
The door knob has a higher thermal conductivity compared to the wooden door and the door knob takes heat away from you hand more than the door does.
The reason a ship made out of iron does not sink is because_____ and ____
The iron ship displaces more water than a compact iron block of the same mass The combined density of iron and air is less than the density of iron alone.
When you apply the first law of thermodynamics to an isobaric expansion of a hot air balloon,
The value of (Q-W) must be greater than zero
According to Archimedes's principle, the buoyancy force acting on an object is equal to what?
The weight of the water the object displaces
The moment of inertia times the rotational acceleration is equal to the net ____, just like the mass of an object times the acceleration is equal to the net force.
Torque
Tor F: When you go swimming and dive under the water, the pressure of the water on the underside of you is greater than the pressure of the water on the topside of you.
True
During a phase change, the temp of a system will be ___ as heat is added
constant
What are the following rotational quantities for the following liner quantities: a v d
a=a v=w d=θ
A tire rotating at constant rotational velocity has zero rotational _____ since the rotational velocity is not changing.
acceleration
A wheel initially rotating at 2 revs per second is slowed down to rotate at only 1 rev per second. During the slowdown the wheel's rotational velocity changed, which means it had rotational _____ as well as rotational velocity
acceleration
The net torque is proportional to the rotational ____ . The proportionality constant is the momentum of inertia
acceleration
Rotational displacement is the quantity that tells what _____ an object has rotated through.
angle
The weight of an object is proportional to it's volume and ____
density
If you are told that your friend has made 7 revolutions on the merry go round, you are being told your friend's rotational____
displacement
A child sitting on a merry go round doubles her distance from the center of rotation. At her her location, her liner speed is _____ what it was prior to moving.
doubled
When under water if you double the depth, the pressure due to the water ___
doubles
Objects immersed in fluid experience an upward buoyant force because the fluid pressure on the bottom of the object is ___ than the pressure on the top of the object.
greater
List three units of rotational velocity
hertz radians per second RPM
If a piece of ice at -5 degrees C is compared to a piece of dry ice at -190 degrees C, the ice seems quite _____ by comparison
hot
If the net change in energy for an ideal gas is negative, what will also decrease
internal energy and kinetic energy
A thermodynamics process in which the pressure remains constant is call ___
isobaric
The weight of an object is proportional to the acceleration of gravity and its ___
mass
When temperature rises one degree on the Celsius scale, on the Fahrenheit scale, the temp will rise___
more than 1 degree
Which of the following conditions must be true in order for rotational momentum to be conserved?
net torque acting on a system is zero (tnet=0)
In an adiabatic process
no exchange of heat takes place during the process
There is a simple relationship to be valid, however, the rotational velocity must be expressed in______per unit time.
radians
Name two units described for angular acceleration
rads/sec2 rmp/s
When water boils the temp __
remains constant
Heat flow by conduction____ Heat flow by convection___ Heat flow by radiation___
requires direct contact between two objects of different temps. requires a medium to circulate hot and cold fluids does not require a medium
A hot air balloon ____ because the average density of the balloon and load is less than the density of air. This is because as the air is heated it expands and the density____
rises decreases
The quantity that describes how fast an object is rotating through some angle is _____ velocity
rotational
The Greek letter theta (θ) is commonly used to represent angles ____________, and the Greek letter omega (ω) is used to represent______________ .
rotational displacements rotational velocities
Name the conservation law with the following conditions: rotational momentum liner momentum energy
rotational momentum = no net torque acting on the system. liner momentum = no net force acting on the system energy = no forces doing work on the system
Rotational acceleration is the rate of change of the
rotational velocity
According to the zeroth law of thermodynamics, if two objects are in contact with each other, they will eventually come to the same___
temperature
In the isothermal process the ____ remains constant
temperature
When holes are drilled at different heights through the wall of a water tower, water will shoot out with larger horizontal velocity closest to the ____
the bottom of the tower.
Joule's experiment demonstrated
the conversion of mechanical work to energy and the conversion of potential energy to heat
Which, if either, will produce the greater torque: a force applied at the end if a wrench handle (perpendicular to the handle) or an equal force applied in the same direction near the middle of the handle?
the force at the end of the wrench
If an object is fully submerged under water, how does the volume of the object compare to the volume of the water displaced.
they are the same
List three rational displacements
three revolutions four radians thirty five degrees
Rotational velocity is the rotational displacement divided by the ______it took for the rotational displacement to happen.
time
True or False: When heat begins to flow between two objects, it will continue to flow until they became the same temp if the objects remain in contact
true
Which equation would be good to find the rotational acceleration if we already knew the initial rotational velocity, the rotational displacement, and the final rotational velocity.
w2=w2+2aθ
The pressure of gas times the its change in volume is the ___done by the gas.
work
Suppose a disk rotates through 13 revolutions in 5 seconds.The disk's displacement is ___ radians? The average rotational velocity is_____
θ= 13 rev × 2π × (rad/1 rev) = 81.6814 rad 81.6814 rad/5 s = 16.3363 rad/s
A merry-go-round is rotating at the rate of 72 rev/min. The rotational velocity in ___ rev/s. Express the rotational velocity in ___ rad/s.
ω= 72 rev/min × (1 min/60 s) = 1.2 rev/s ω= 72 rev/min × (1 min ×2⋅π rad/60 s ×1 rev) = 7.5398 rad/s
When one of the authors was a teenager, the rate of rotation for popular music records on a record player was 78 RPM. The rotational velocity in rev/s is____? The number of revolutions made in 5 s is_____
ω=(78 RPM)×1 min/60 s = 1.3 rev/s (78 RPM)×(1 min/60 s) × 5 s = 6.5
