AP Physics Multiple Choice Review

A ball of mass m is found to have a weight Wx on Planet X. Which of the following is a correct expression for the gravitational field strength of Planet X?

The gravitational field strength of Planet XX is Wx/m.

An astronaut with mass MA is within a satellite that orbits Earth at a height H above its surface. Earth has a mass ME and radius RE. Which of the following is a correct expression for the gravitational force exerted on the astronaut by Earth?

Fg=G(MgMa/(Re+H)^2)

A student performs an experiment that involves the motion of a pendulum. The student attaches one end of a string to an object of mass M and secures the other end of the string so that the object is at rest as it hangs from the string. When the student raises the object to a height above its lowest point and releases it from rest, the object undergoes simple harmonic motion. As the student collects data about the time it takes for the pendulum to undergo one oscillation, the student observes that the time for one swing significantly changes after each oscillation. The student wants to conduct the experiment a second time. Which two of the following procedures should the student consider when conducting the second experiment?

Make sure that the difference in height between the pendulum's release position and rest position is not too large. Make sure that the experiment is conducted in an environment that has minimal wind resistance.

A student wants to study the motion of an object that has a constant acceleration. Which of the following experiments could the student conduct to provide the best situations in which an object has a constant acceleration? Select two answers.

Release a ball from rest near Earth's surface. Release a cart from rest such that it travels down an incline of 40° with respect to the ground.

A 4 kg block is pushed up an incline that makes a 30o angle with the horizontal. Once the block is pushed a distance of d=5.0 m up the incline, the block remains at rest. What is the approximate change in the gravitational potential energy of the block-Earth system when the block is held at rest compared to its original location at the bottom of the incline?

100J

A 3kg horizontal disk of radius 0.2m rotates about its center with an angular velocity of 50rad/s. The edge of the horizontal disk is placed in contact with a wall, and the disk comes to rest after 10s. Which of the following situations associated with linear impulse is analogous to the angular impulse that is described?

A 3kg block is initially traveling at 10m/s. The block encounters a 3N frictional force until the block eventually stops.

An astronaut in deep space is at rest relative to a nearby space station. The astronaut needs to return to the space station. A student makes the following claim: "The astronaut should position her feet pointing away from the space station. Then, she should repeatedly move her feet in the opposite direction to each other. This action will propel the astronaut toward the space station." Is the student's claim correct? Justify your selection.

No. The astronaut's feet are not exerting a force on another object, so there is no external force to accelerate the astronaut toward the space station.

An object of mass 5kg travels in the positive direction with a speed of 1m/s. The object collides with a second object that exerts an average net force over an interval of time such that the 5kg object comes to rest. Which of the following best predicts the change in momentum for the 5kg object?

The change in momentum is in the negative direction.

A ball is released from rest from the twentieth floor of a building. After 1 s, the ball has fallen one floor such that it is directly outside the nineteenth-floor window. The floors are evenly spaced. Assume air resistance is negligible. What is the number of floors the ball would fall in 3s after it is released from the twentieth floor?

7 to 10 floors

Block X of mass 4M travels at a speed 5v0 toward block Y of mass M, which is initially at rest. After block X elastically collides with block Y, block X has a speed of 3v0 in the same direction as before the collision. What is the speed of block Y immediately after the collision?

8v0

One end of a string is attached to an object of mass M, and the other end of the string is secured so that the object is at rest as it hangs from the string. When the object is raised to a position X that is a height H above its lowest point and released from rest, the object undergoes simple harmonic motion. When the object passes through the equilibrium position Y, it has a speed v0. Which of the following methods could a student use to determine the total mechanical energy E at position Y, and why?

E=12Mv20, because this equation represents the maximum kinetic energy of the pendulum at position Y if the system has zero gravitational potential energy at position Y. E=MgH, because this equation represents the maximum gravitational potential energy of the system at position X if the system has zero gravitational potential energy at position Y.

A moon orbits an isolated planet in deep space. Which of the following forces that the planet exerts on the moon can be considered as negligible?

The electric force

A car initially at rest accelerates at 10m/s^2. The car's speed after it has traveled 25 meters is most nearly

22.0 m/s

A student is at rest on a stool that may freely spin about its central axis of rotation. As the stool spins, the student holds onto two dumbbells as the stool spins at an angular speed of 1.2 rad/s with the student's arms completely stretched out from the student's body. At this instant, the student-dumbbell system has rotational inertia of 6 kg⋅m^2. The student then brings their arms close to their body, and rotational inertia of the student-dumbbell system is changed to 2 kg⋅m^2. What is the new angular speed of the student?

3.6 rad/s

A 2kg object is released from rest near the surface of a planet such that its gravitational field is considered to be constant. The mass of the planet is unknown. The object's speed after falling for 3 s is 75 m/s. Air resistance is considered to be negligible. Calculate the weight of the 2kg object on the planet of unknown mass.

50N

In an experiment, a solid, uniform sphere is at rest on a horizontal surface. A net force is applied tangentially to the edge of the sphere that is the greatest horizontal distance away from the central axis of the sphere. The sphere begins to rotate from rest until the force is no longer applied after 3s. Frictional forces between the sphere and the horizontal surface are considered to be negligible. Which two of the following quantities, when used together, could a student measure to determine the change in angular momentum of the sphere from 0s to 3s?

Average net force exerted on the sphere from 0s0s to 3s. Radius of the sphere

A uniform ladder of mass M and length L rests against a smooth wall at an angle θ0. What is the torque due to the weight of the ladder about its base?

MgL cos (θ0)/2

An object travels down a ramp at a constant acceleration. The object experiences a force of friction and a gravitational force. Which of the following could be true about the motion of the object?

The force of friction between the surface and the object is less than the component of the gravitational force that is parallel to the ramp.

A student wants to approximate the amount of work that the force due to gravity does on the student as the student walks up a set of stairs. Which of the following measurements must the student collect in order to approximate the amount of work done by Earth on the student?

The mass of the student. The final vertical height above the initial vertical position.

A student drops an object from rest above a force plate that records information about the force exerted on the object as a function of time during the time interval in which the object is in contact with the force plate. Which of the following measurements should the student take, in addition to the measurements from the force plate, to determine the change in momentum of the object from immediately before the collision to immediately after the collision?

The student has enough information to make the determination.

An object is released from rest near and above Earth's surface from a distance of 10m. After applying the appropriate kinematic equation, a student predicts that it will take 1.43s for the object to reach the ground with a speed of 14.3m/s . After performing the experiment, it is found that the object reaches the ground after a time of 3.2s. How should the student determine the actual speed of the object when it reaches the ground? Assume that the acceleration of the object is constant as it falls.

Use y = y0+vy0t+12ayt2y = y0+vy0t+12ayt2 to determine the acceleration of the object as it falls since all other quantities are known. Then use mgy0−WExternal = 12mv2f with WExternal = may(yf−y0) since all other quantities are known. Solve for vy

Object X of mass 4 kg travels with a speed of 3 ms toward object Y of mass 2 kg that is initially at rest. Object X then collides with and sticks to object Y. After the collision, object X and object Y remain stuck together. How much mechanical energy is converted into nonmechanical energy during the collision?

6 J

A tennis ball is thrown against a vertical concrete wall that is fixed to the ground. The ball bounces off the wall. How does the force exerted by the ball on the wall compare with the force exerted by the wall on the ball?

The forces exerted by the ball and the wall have the same magnitude.

A cart with an unknown mass is at rest on one side of a track. A student must find the mass of the cart by using Newton's second law. The student attaches a force probe to the cart and pulls it while keeping the force constant. A motion detector rests on the opposite end of the track to record the acceleration of the cart as it is pulled. The student uses the measured force and acceleration values and determines that the cart's mass is 0.4kg. When placed on a balance, the cart's mass is found to be 0.5kg. Which of the following could explain the difference in mass?

The track was not level and was tilted slightly downward.

A satellite of mass m orbits a moon of mass M in uniform circular motion with a constant tangential speed of v. The gravitational field strength at a distance R from the center of moon is gR. The satellite is moved to a new circular orbit that is 2R from the center of the moon. What is the gravitational field strength of the moon at this new distance?

gR/4

Two identical wheels, wheel 1 and wheel 2, initially at rest begin to rotate with constant angular accelerations α. After rotating through the same angular displacement, Δθ0 , the angular velocity of wheel 1 is ω1 and the angular velocity of wheel 2 is ω2=3ω1 . How does the angular acceleration of wheel 2, α2, compare to the angular acceleration of wheel 1, α1 ?

α2=9α1

Consider a system of two objects and Earth. Object X and object Y are held together by a light string. MY is larger than MX. The two-object system is released from rest in the orientation shown in the figure at a height H above Earth's surface. The change in the kinetic energy of the system from when it is released to the instant it hits the ground is most nearly

(MY+MX)gH

A student must determine a nonzero change in momentum of an object for a specific interval of time. Which of the following experiments could the student conduct?

Drop a ball of known mass above a motion detector, and record the final speed of the ball before it reaches the motion sensor. Give a block of known mass an initial velocity so that it slides across a rough surface in front of a motion detector, slows down, and eventually stops. Use the motion detector to record the initial velocity of the block.

The center of mass of a uniform meterstick is placed on a fulcrum. Two objects of known mass, m1 and m2, are hung at known positions on the meterstick. One end of a string is attached to one end of the meterstick, and the other end of the string is looped around a pulley and connected to hanging object X of unknown mass. The meterstick does not rotate and is level with the horizontal. Which of the following measuring devices, if any, should be used to make measurements to determine the unknown mass of object X? Justify your selection.

No additional equipment or measurements are needed, because the force due to gravity exerted on objects m1 and m2 and the distance between where the force is applied and the tip of the fulcrum are already known.

A student must determine the relationship between the inertial mass of an object, the net force exerted on the object, and the object's acceleration. The student uses the following procedure. The object is known to have an inertial mass of 1.0kg. Step 1: Place the object on a horizontal surface such that frictional forces can be considered to be negligible. Step 2: Attach a force probe to the object. Step 3: Hang a motion detector above the object so that the front of the motion detector is pointed toward the object and is perpendicular to the direction that the object can travel along the surface. Step 4: Use the force probe to pull the object across the horizontal surface with a constant force as the force probe measures force exerted on the object. At the same time, use the motion detector to record the velocity of the object as a function of time. Step 5: Repeat the experiment so that the object is pulled with a different constant force. Can the student determine the relationship using this experimental procedure?

No, because the motion detector should be oriented so that the object moves parallel to the line along which the front of the motion detector is aimed.

Disk Y of rotational inertia IY=12MYR2Y about its center is held at rest above disk X of rotational inertia IX=12MXR2Y about its center. Disk X initially rotates about its center with an angular velocity of +ω0. Disk Y is then slowly lowered onto disk X until both disks are in contact and rotate together with a common angular velocity. Which two of the following predictions are correct about the angular momentum of disk X and disk Y immediately before and after the rotational collision?

The angular momentum of the disk X-disk Y system immediately after the collision is equal to the angular momentum of the system immediately before the collision. The angular momentum of disk Y immediately after the collision is greater than the angular momentum of disk Y immediately before the collision.

A student uses both hands to push a door such that it moves and swings open after the force has been applied. The student then makes the following claim: "I can use both of my hands to apply a constant force on my body so that my body falls backward." Which of the following statements correctly justifies the student's claim?

The claim is not correct because the student's body will exert a force of equal magnitude back on the student's hands as a result of Newton's third law of motion.

A ball is moved from Earth to a planet that has a gravitational acceleration that is double that of Earth. How does the gravitational force on the ball when it is on the new planet compare to the gravitational force on the ball when it is on Earth?

The gravitational force on the ball when it is on the new planet is double the force on the ball when it is on Earth.

A student predicts that a block sliding down a ramp inclined at 45 degrees should have an acceleration of approximately 7 m/s2. The block is released from rest, and the student measures the distance the block travels and the time it takes to travel that distance. The student determines that the block's acceleration is only 5.5 m/s2. Which of the following is the most likely reason for the difference between the predicted and calculated accelerations?

The student's model used to make the prediction did not account for all of the forces that are exerted on the block.

An object is released from rest at a height H near and above the surface of Earth. As the object falls toward the surface, Earth's atmosphere exerts a resistive force on the object such that it reaches a terminal velocity before it reaches the ground. Which of the following claims is true?

The system consisting of only the object is an open system. Earth's atmosphere does negative work on the object as it falls toward the surface.

In one experiment, a student rolls a 2 kg ball such that it collides with a wall with a force of 10,000 N. In a second experiment, the student rolls a 5 kg ball such that it collides with the wall at a force of 5000 N. In both experiments, the balls bounce back from the wall and eventually come to rest. Which of the following statements is true regarding the force that the wall exerts on each ball?

The wall exerts a greater force on the 2 kg ball than on the 5 kg ball since the force from the wall on each ball is equal to the force that each ball exerts on the wall.

Two students want to determine the speed at which a ball is released when thrown vertically upward into the air. One student throws the ball into the air while the other student measures the total time that the ball is in the air. The students use a meterstick to measure the release height of the ball. Which of the following equations should the students use to determine the speed at which the ball was released?

Use y=y0+vy0t+12ayt2y=y0+vy0t+12ayt2 from the moment in time in which the ball was released to the moment in time in which the ball hits the ground.

A student is provided with a battery-powered toy car that the manufacturer claims will always operate at a constant speed. The student must design an experiment in order to test the validity of the claim. Which of the following measuring tools can the student use to test the validity of the claim?

Photogates placed at the beginning, end, and at various locations along the track that the car travels on ans A meterstick to measure the distance of the track that the car travels on

One end of a string is attached to an object of mass M, and the other end of the string is secured so that the object is at rest as it hangs from the string. When the object is raised to a height above its lowest point and released from rest, the object undergoes simple harmonic motion with a frequency f0. In a second scenario, the length of the string is cut in half before the object undergoes simple harmonic motion again. What is the new frequency of oscillation of the object in terms of f0?

square root of 2 x f0

A student must conduct an experiment in which a block is pulled across a horizontal surface by a spring scale so that a nonzero change in momentum of the block can be determined for a specific time interval. The student also has access to measuring tools that are found in a typical physics laboratory. Which of the following experiments could the student conduct to determine the change in momentum of the cart?

Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block.

A student attaches a block to a vertical spring so that the block-spring system will oscillate if the block-spring system is released from rest at a vertical position that is not the system's equilibrium position. The system oscillates near Earth's surface. The system is then taken to the Moon's surface, where the gravitational field strength is nearly 1/6 that of the gravitational field strength near Earth's surface. Which of the following claims is correct about the period of oscillation for the system?

The system has the same period on Earth as the Moon.

A block of mass M is sliding with an initial speed vi along a horizontal surface with negligible friction. A constant force of magnitude FA is exerted on the object at an upward angle of 60∘ from the horizontal, causing the object to speed up. If the block remains in contact with the floor, what is the change in the block's kinetic energy as it moves a horizontal distance Δx ?

1/2(FAΔx)

A student attaches a block of mass M to a vertical spring so that the block-spring system will oscillate if the block-spring system is released from rest at a vertical distance D below the system's equilibrium position. The student measures the period of oscillation for the system to be P. What is the maximum spring potential energy of the system Us in terms of D, M, and P ?

2M(pi^2)D^2/p^2

A student must analyze data collected from an experiment in which a block of mass 2M traveling with a speed v0 collides with a block of mass M that is initially at rest. After the collision, the two blocks stick together. Which of the following applications of the equation for the conservation of momentum represent the initial and final momentum of the system for a completely inelastic collision between the blocks? Justify your selection.

2Mv0=3Mvf, because the blocks stick together after the collision. 2Mv0=2Mvf+Mvf, because the blocks stick together after the collision.

A 2 kg object is a distance of 10,000,000 m away from the center of Earth, which has a mass of nearly 6×10^24 kg. What is the approximate gravitational field strength of Earth's gravitational field at the location of the 10 kg object?

4 N/kg

Ball X of mass 1.0kg and ball Y of mass 0.5kg travel toward each other on a horizontal surface. Both balls travel with a constant speed of 5m/s until they collide. During the collision, ball Y exerts an average force with a magnitude of 40N for 16 s on ball X. Which of the following best predicts ball Y's momentum after the collision?

Ball Y will travel at a speed greater than 5m/s in the opposite direction of travel as before the collision.

The Atwood's machine shown consists of two blocks of mass m1 and m2 that are connected by a light string that passes over a pulley of negligible friction and negligible mass. The block of mass m1 is a distance h1 above the ground, and the block of mass m2 is a distance h2 above the ground. m2 is larger than m1. The two-block system is released from rest. Which of the following claims correctly describes the outcome after the blocks are released from rest but before the block of m2 reaches the ground?

For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to the work done by gravity on the system. For the system consisting of the two blocks, the pulley, and Earth, the change in the total mechanical energy of the system is zero.

A satellite is a large distance from a planet, and the gravitational force from the planet is the only significant force exerted on the satellite. The satellite begins falling toward the planet, eventually colliding with the surface of the planet. As the satellite falls, which of the following claims is correct about how the force that the planet exerts on the satellite Fps changes and how the force that the satellite exerts on the planet Fsp changes, if at all? What reasoning supports this claim?

Fps and Fsp both increase. The gravitational forces that two objects exert on one another decrease as the separation between the objects increases, and these forces are always equal in magnitude.

An object of known mass M with speed v0 travels toward a wall. The object collides with it and bounces away from the wall in the opposite direction in which the object was initially traveling. The wall exerts an average force F0 on the object during the collision. A student must use the equation Δp⃗ =F⃗ Δt to determine the change in momentum of the object from immediately before the collision to immediately after the collision. Which side of the equation could the student use to determine the change of the object's momentum?

Neither side of the equation may be used because there are too many unknown quantities before, during, and after the collision.

A student must design an experiment to determine the gravitational mass of an object. Which of the following experiments could the student use?

Place the object on one side of a lever at a known distance away from a fulcrum. Place known masses on the other side of the fulcrum so that they are also placed on the lever at known distances from the fulcrum. Move the known masses to a known distance such that the lever is in static equilibrium. Place the object on the end of a vertically hanging spring with a known spring constant. Allow the spring to stretch to a new equilibrium position, and measure the distance the spring is stretched from its original equilibrium position.

A student must design an experiment to determine the relationship between the mass of an object and the resulting acceleration when the object is under the influence of a net force. Which of the following experiments should the student conduct in order to determine the relationship between all three quantities?

Slide objects of different masses across the same rough surface so that each object travels at a constant speed while under the influence of the force of kinetic friction. Then measure the force required to keep each object at a constant speed by using a force sensor, and record the mass of each object by using a mass scale. Perform this experiment multiple times with objects of different masses.

A student conducts an experiment in which an object is released from rest above a motion detector so that data can be collected about the object's motion as the object falls to the ground. The experiment is conducted near Earth's surface. All frictional forces are considered to be negligible unless otherwise stated. The student wants to collect data to determine the work done by the force due to gravity on the object as it falls. Which of the following lists contains the fewest number of measuring devices, in addition to the motion detector, that the student can use?

Spring Scale

A student must determine how the mass of a block affects the period of oscillation when the block is attached to a vertical spring. The value of the spring constant is known. The student writes the following experimental procedure. 1. Use an electronic balance to measure the mass of the block. 2. Attach the block to the vertical spring. 3. Displace the block from the system's equilibrium position to a new vertical position. 4. Release the block from rest. 5. Use a meterstick to measure the vertical displacement of the center of mass of the block from the system's equilibrium position to its maximum vertical position above the equilibrium position. 6. Use a stopwatch to measure the time it takes for the system to make ten complete oscillations. 7. Repeat the experiment for different vertical displacements and block masses. Which of the following steps of the procedure should the student revise to make the determination? Justify your selection.

Step 7, because the experiment should not be repeated for different vertical displacements and block masses.

A satellite of mass m orbits a moon of mass M in uniform circular motion with a constant tangential speed of v. The satellite orbits at a distance R from the center of the moon. Which of the following is a correct expression for the time T it takes the satellite to make one complete revolution around the moon?

T=2pi x the square root of (R^3/GM)

A ball, of mass 1.0kg, is released from rest above a horizontal surface. The ball falls downward and collides with the surface with a speed of 2.0m/s. The average force exerted during the collision is 20N over a time interval of 0.1s. Which of the following best predicts what will happen to the ball immediately after the collision?

The ball will come to rest on the surface.

A book is at rest on the top of a table. A student makes the following claim: "An attractive electromagnetic force is exerted on the book from the table, and this force can also be classified as the normal force." Which of the following statements correctly justifies the student's claim?

The claim is incorrect because the charged particles of the table exert an upward repulsive force on the charged particles of the book.

A ball is dropped onto the floor and bounces upward. Which of the following claims are correct about the force that the ball exerts on the floor compared to the force that the floor exerts on the ball when the ball and the floor are in contact?

The magnitude of the forces exerted by both objects is the same because the ball and the floor cannot exert forces of different magnitudes on each other.

In an experiment, an object is released from rest near and above Earth's surface. A student must determine the relationship between the direction of the gravitational force exerted on the object and the change in momentum caused by that force. What data could the student collect to determine the magnitude and direction of the gravitational force and the change in momentum of the object? Justify your choices. Select two answers.

The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the velocity of the object the instant before it reaches Earth's surface, because it is required to determine the change in velocity of the object. The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the distance fallen by the object, because the force is exerted during the entire falling distance.