Physics Final Multiple Choice
A rider in a "barrel of fun" finds herself stuck with her back to the wall and her feet above the floor of the rotating "barrel." Which diagram correctly shows the forces acting on her?
A
A ball drops some distance and gains 30 J of kinetic energy. Do NOT ignore air resistance. How much gravitational potential energy did the ball lose?
A) more than 30 J
Consider an object that floats in water but sinks in oil. When the object floats in water, half of it is submerged. If we slowly pour oil on top of the water so it completely covers the object, the object
A) moves upward relative to the water surface
A uniform solid cylinder made of lead has the same mass and the same length as a uniform solid cylinder made of wood. The rotational inertia of the lead cylinder compared to the wooden one is:
A) smaller because the radius of the lead cylinder will be smaller
A copper ring has a radius of 50 mm. A small gap of 3.00 mm is taken out of the ring. When the ring is heated by 75 degrees Celsius,
A) the gap becomes smaller than 3.00 mm
Consider these situations: (i) a ball moving at speed v is brought to rest; (ii) the same ball is projected from rest so that it moves at speed v; (iii) the same ball moving at speed v is brought to rest and then projected backward to its original speed. In which case(s) does the ball undergo the smallest change in momentum?
B) cases (i) and (ii)
The second law of thermodynamics leads us to conclude that
B) disorder in the universe is increasing with the passage of time.
A figure skater stands on one spot on the ice (assumed frictionless) and spins around with her arms extended. When she pulls in her arms, she reduces her rotational inertia and her angular speed increases so that her angular momentum is conserved. Compared to her initial rotational kinetic energy, her rotational kinetic energy after she has pulled in her arms must be:
B) larger, because she is rotating faster.
When a fixed amount of ideal gas goes through an isothermal expansion
B) the gas does no work.
Why is the coefficient of friction a unitless quantity?
Because it is the ratio of the friction force and the normal force acting on an object
A solid iron anchor with density 7850 kg/m3 has an apparent weight when fully submerged in water that is several hundred newtons less than its weight in air. This is because:
C) a buoyant force equal to the weight of displaced water acts on it.
When a vapor condenses
C) heat energy leaves the substance.
If the temperature of a fixed amount of an ideal gas is increased, it NECESSARILY follows that
C) the speed of the gas molecules will increase.
A block initially at rest is allowed to slide down a frictionless ramp and attains a speed v at the bottom. To achieve a speed 2v at the bottom, how many times as high must a new ramp be?
D) 4
In a perfectly ELASTIC collision between two objects
D) both the momentum and the kinetic energy of the system are conserved.
A baseball is thrown vertically upward and feels no air resistance. As it is rising
D) its momentum is not conserved, but its mechanical energy is conserved.
A golf ball is fired at a bowling ball initially at rest, and bounces back elastically. Compared to the bowling ball, the golf ball after the collision has
D) less momentum but more kinetic energy
Two marbles, one twice as heavy as the other, are dropped to the ground from the roof of a building. Just before hitting the ground, the heavier marble has
D) twice as much kinetic energy as the lighter one.
Oil of density 825 kg/m3 flows through a pipeline that changes elevation as it follows the local terrain and occasionally changes diameter by as much as 10%. The pressure in the pipeline can be found by using:
E) Bernoulli's equation
Two steel spheres are made of the same material and have the same diameter at room temperature, but one is solid and the other is hollow. They are both placed in an industrial oven and heated to the same temperature. Which of the following is true?
E) The two spheres remain of equal size.
The rate of heat energy radiated by a hot object does NOT depend upon:
E) Wrong! Radiation depends upon all of these factors.
The number of molecules in one mole of a substance
E) is the same for all substances.
A solid disk and a hollow sphere roll down an incline. The sphere is slower than the disk if
The sphere is always slower regardless of the relative values of m and r
A rigid object is rotating about a fixed axis rotation through the center of mass of the object. The object has a constant angular acceleration, +alpha. Which one of the following statements about the objects is true?
The total acceleration of the object increases as omega increases
What happens to the thermal energy and entropy of a system at absolute zero?
a) Both go to zero.
For a monatomic ideal gas, which three macroscopic parameters determine how the entropy of the system changes as the gas changes from one equilibrium state to a different equilibrium state?
a) Change in the absolute pressure b) Change in the absolute temperature c) Change in the volume of the gas
For a monatomic ideal gas, which three macroscopic parameters determine how the entropy of the system changes as the gas changes from one equilibrium state to a different equilibrium state? Indicate all three.
a) Change in the absolute temperature, b) Change in the absolute pressure, f) Change in the volume of the gas
Looking at the figure to the right, is the interaction elastic, inelastic, or totally inelastic?
a) Elastic, because both carts are moving after the collision
According to the Eth = W + Q form of the energy law, what is the sign of the change in the thermal energy of an ideal gas in an isochoric process where thermal energy is added to the system? What is the sign of change in the thermal energy for an isentropic expansion process?
a) Positive, positive
In lab, a rotating apparatus has 3 pulleys of different radius. For an experiment, a string wrapped around the smallest radius pulley and attached to a 300 gram falling mass produces an angular acceleration of 2.95 rad/s2. What will result if the string is wrapped around the center pulley (larger radius pulley) and the same falling mass is used? Circle all that apply:
a) The moment of inertia remains the same., f) The applied torque decreases., h) The angular acceleration decreases.
At one particular moment, a subway train is moving with a positive velocity and positive acceleration. Which of the following phrases best describes the motion of this train? Assume the front of the train is pointing in the positive x direction.
a) The train is moving faster as it moves forward.
If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.
a) True
An object is located inside a thin spherical shell of uniform density. At what locations would the net gravitational force due to the shell of matter be zero?
a) anywhere within the shell
The rotational inertia of a rigid body
a) depends on the location of the axis of rotation, b) is a measure of its resistance to changes in its rotational motion
A crate is being pulled up an inclined ramp at a constant speed of 0.75 m/s. The friction force acting on the crate must be directed
a) down the ramp
You slam on the brakes of your car in a panic stop, and skid for a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?
a) four times as far
Consider a person standing in an elevator that is accelerating upward. The upward normal force N exerted by the elevator floor on the person is the downward weight W of the person.
a) larger than
Consider an object that floats in water but sinks in oil. When the object floats in water, half of it is submerged. If we slowly pour oil on top of the water so it completely covers the object, the object
a) moves upward relative to the water surface
The average molecular kinetic energy of a gas can be determined by knowing
a) only the temperature of the gas
A uniform solid cylinder made of lead has the same mass and the same length as a uniform solid cylinder made of wood. The rotational inertia of the lead cylinder compared to the wooden one is:
a) smaller because the radius of the lead cylinder will be smaller
The rotational inertia of a wheel about its axle does not depend upon its:
a) speed of rotation
Looking at the figure below, which cart has the smaller inertia value?
a) standard cart
The internal energy of an ideal gas depends on:
a) the temperature only
What is the direction of the rotational velocity vector for the minute hand of a clock hanging on the wall?
away from the observer
A certain metal has a coefficient of linear expansion of α. For this metal, the coefficient of volume expansion will be
b) 3α
What are two advantages of the Brayton cycle over the Carnot cycle? Indicate both.
b) It produces more mechanical energy., e) Its power output is greater.
What are two advantages of the Brayton cycle over the Carnot cycle?
b) Its power output is greater., d) It produces more mechanical energy per cycle.
A 1.0-kg block and a 2.0-kg block are pressed together on a horizontal frictionless surface with a compressed very light spring between them. They are not attached to the spring. After they are released and have both moved free of the spring (more than one may apply; choose all that are correct)
b) both blocks will have equal magnitudes of momentum., e) the heavier block will have less kinetic energy than the lighter block.
An object rests on an inclined surface. If the inclination of the surface is made steeper, the normal force acting on the object
b) decreases
In simple harmonic motion, the acceleration is maximum when the:
b) displacement is maximum
The figure shows the velocity of a particle as it travels along the x-axis. What is the direction of the acceleration at t = 0.4 s?
b) in the -x direction
Two cubes of solid metal, one of iron and the other of aluminum, have the same mass. When placed in water, the buoyant force
b) is greater on the aluminum cube because it has a larger volume.
Two cubes of solid metal, one of iron and the other of aluminum, have the same volume. When placed in water, the buoyant force
b) is greater on the aluminum cube because it has a smaller mass
A particle moves back and forth along the x axis from x = -xm to x = +xm, in simple harmonic motion with period T. At time t = 0 it is at x = +xm. When t = 0.35T:
b) it is at x = 0 and is traveling toward x = -xm
A particle moves back and forth along the x axis from x = -xm to x = +xm, in simple harmonic motion with period T. At time t = 0 it is at x = +xm. When t = 0.35T:
b) it is at x = 0 and is traveling toward x = -xm
A figure skater stands on one spot on the ice (assumed frictionless) and spins around with her arms extended. When she pulls in her arms, she reduces her rotational inertia and her angular speed increases so that her angular momentum is conserved. Compared to her initial rotational kinetic energy, her rotational kinetic energy after she has pulled in her arms must be:
b) larger, because she is rotating faster.
A student kicks a soccer ball in a high arc toward the goal. At the highest point in its trajectory
b) neither the ball's velocity nor its acceleration is zero
When a fixed amount of ideal gas goes through an isothermal expansion
b) no work, positive or negative, is done on the gas.
Two carts are about to collide head-on on a track. The inertia of cart 1 is greater than the inertia of cart 2, and the collision is inelastic with a coefficient of restitution of 80%. The speed of cart 1 before the collision is higher than the speed of cart 2 before the collision. Which cart has the greater change in momentum due to the collision?
c) Both carts have the same magnitude of momentum change
How does the entropy of a system change when it undergoes a quasistatic adiabatic process?
c) It stays the same
The moment of inertia of a rigid body about a fixed axis through its center of mass is I. The moment of inertia of this same body about a parallel axis through some other point is always:
c) Larger than I
According to the Eth = W + Q form of the energy law, what is the sign of the change in the thermal energy of an ideal gas in an isochoric process where thermal energy is added to the system? What is the sign of change in an isentropic expansion process?
c) Positive, positive
Two masses, m1 and m2, are connected to each other as shown in the figure. Mass m1 slides without friction on the table surface. Both masses have acceleration of magnitude a as shown. How does the tension in the string compare to the weight, m2g, of mass m2?
c) The tension is smaller than m2g.
A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater height?
c) They both slide to the same height because they have the same velocity.
A solid iron anchor with density 7850 kg/m3 has an apparent weight when fully submerged in water that is several hundred Newtons less than its weight in air. This is because:
c) a buoyant force equal to the weight of displaced water acts on it
Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be
c) less than F but not zero.
Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be
c) less than F but not zero.
In a PERFECTLY INELASTIC collision between two objects
c) the momentum of the system is conserved but the kinetic energy of the system is not conserved.
If the temperature of a fixed amount of an ideal gas is increased, it NECESSARILY follows that
c) the speed of the gas molecules will increase
If the temperature of a fixed amount of an ideal gas is increased, it NECESSARILY follows that
c) the speed of the gas molecules will increase.
A block initially at rest is allowed to slide down a frictionless ramp and attains a speed v at the bottom. To achieve a speed 2v at the bottom, how many times as high must a new ramp be?
d) 4
A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point mass m a distance d from the center of the shell, outside the shell (d > R2), is:
d) GMm/d^2
On which variables does the work done on an ideal gas depend? Answer all that apply
d) P (pressure), c) V (volume)
On which variables does the work done on an ideal gas depend? Answer all that apply.
d) P (pressure), c) V (volume)
An ideal gas undergoes an isentropic expansion from state A to state B. In this process, which of the following is true? (Use sign conventions from class.)
d) Q > 0, ΔEth = 0, W > 0
When an object experiences uniform circular motion, the direction of the acceleration vector is
d) directed toward the center of the circular path
Identical forces act for the same length of time on two different masses. The change in momentum of the smaller mass is
d) equal to the change in momentum of the larger mass
What does the word "normal" mean in the phrase "normal force"?
d) the component of the surface force that is perpendicular to the surface
A wheel starts with initial angular velocity and slows with a constant angular acceleration. As time goes on the acceleration vector for a point on the rim:
decreases in magnitude and becomes more nearly tangent to the rim
The number of seconds in one day is 86,400. Express this as an order of magnitude value
e) 10^5s
Oil of density 825 kg/m3 flows through a pipeline that changes elevation as it follows the local terrain and occasionally changes diameter by as much as 10%. The pressure in the pipeline can be found by using:
e) Bernoulli's equation
Consider the rotating system used in lab last week, with a descending mass on a string wrapped around a pulley to accelerate the system. What will change if the inertia of the descending mass is increased?
e) Torque, angular acceleration, and moment of inertia will all decrease
If we double only the mass of a vibrating ideal mass-and-spring system, the mechanical energy of the system
e) does not change.
If we double only the mass of a vibrating ideal mass-and-spring system, the mechanical energy of the system
e) does not change.
What is the physical quantity found by taking the area under a force vs. time curve?
e) impulse
The number of molecules in one mole of a substance
e) is the same for all substances.
An airplane banks at 35° to the horizontal as it turns. What forces act on the airplane?
e) only thrust, drag, lift, gravity, and centripetal force
The rotational inertia of a wheel about its axle does not depend upon its:
e) speed of rotation
A 1.0-kg block and a 2.0-kg block are pressed together on a horizontal frictionless surface with a compressed very light spring between them. They are not attached to the spring. After they are released and have both moved free of the spring (more than one may apply; choose all that are correct)
e) the heavier block will have less kinetic energy than the lighter block.
What is the physical quantity found by taking the area under a force vs. position curve?
e) work
Consider these situations: (i) a ball moving at speed v is brought to rest; (ii) the same ball is projected from rest so that it moves at speed v; (iii) the same ball moving at speed v is brought to rest and then projected backward to its original speed. In which case(s) does the ball undergo the largest change in momentum?
f) case (iii)
If two gears of different diameters are in contact, with their teeth meshing, what do they have in common?
tangential speed vt of the teeth
The angular momentum of a system remains constant
when no external torque acts on the system
A 50-cm3 block of wood is floating partially submerged in water, and a 50-cm3 block of brass is totally submerged in water. Which block has the greater buoyant force acting on it?
b) the brass because it displaces more water
Two uniform circular disks having the same mass and the same thickness are made from different materials. The disk with the larger rotational inertia is:
b) the one made from the less dense material
