AP Physics study questions

Box A of mass m sits on the floor of an elevator, with box B of mass 2m on top of it, as shown in the figure above. The elevator is moving upward and slowing down. FA is the magnitude of the force exerted on box A by box B, FB is the magnitude of the force exerted on box B by box A, and Fg is the magnitude of the gravitational force exerted on box B. Which of the following ranks the forces in order of increasing magnitude?

(FB = FA) < Fg

The graph above shows the position x as a function of time for the center of mass of a system of particles of total mass 6.0 kg. For a very short time interval around 2.0 s, an external force is exerted on an object in the system. What is the resulting change in momentum of the system?

-18 kg×m/s

A 1.0 kg lump of clay is sliding to the right on a frictionless surface with speed 2 m s . It collides head-on and sticks to a 0.5 kg metal sphere that is sliding to the left with speed 4 m s . What is the kinetic energy of the combined objects after the collision?

0 J

An object with mass m is suspended at rest from a spring with a spring constant of 200 N m . The length of the spring is 5.0 cm longer than its unstretched length L, as shown above. A person then exerts a force on the object and stretches the spring an additional 5.0 cm. What is the total energy stored in the spring at the new stretched length?

1.0 J

A 50 kg athlete running at speed v grabs a light rope that hangs from a 10-meter-high platform and swings to a maximum of 1.8 m above the ground. Later, a 100 kg athlete, running at the same speed, grabs a similar rope hanging from a 5-meter-high platform. What is the maximum height to which the 100 kg athlete swings?

1.8 m

The spring constant of the spring is approximately which of the following?

100 N/m

To analyze the characteristics and performance of the brakes on a 1500 kg car, researchers collected the data shown in the table above. It shows the car's speed when the brakes are first applied and the corresponding braking distance required to stop the car. The magnitude of the average braking force on the car is most nearly

12,000 N

For another identical object initially at rest, no frictional force is exerted during segment 2 (between t = 2 s and t = 4 s). A rope exerts the same constant force of magnitude FT as in the previous scenario. What is the change in the object's kinetic energy during segment 2?

12.0 J

Object A has mass 2 kg and is traveling to the right at speed 3 m/s. Object B is traveling to the left at 3 m/s. The objects collide head-on, and afterward each has a speed of 3 m/s. Which of the following could be the mass of object B ? Select two answers.

2 kg negligible compared to 2 kg

Two identical blocks with mass 5.0 kg each are connected to the opposite ends of a compressed spring. The blocks initially slide together on a frictionless surface with velocity 2 m s to the right. The spring is then released by remote control. At some later instant, the left block is moving at 1 m s to the left, and the other block is moving to the right. What is the speed of the center of mass of the system at that instant?

2 m/s

If the block is sliding up section 2, what is the magnitude of the force of friction that is exerted on the block by the incline?

2µkMgcosθ

A 9.0 V battery and two resistors are connected in the circuit shown above. The current through the 3.0Ω resistor is 2.0 A. What is the potential difference across resistor R2 ?

3.0 V

A 0.050 kg tennis ball is moving to the left at 10 m s when it is hit by a tennis racket that is moving to the right. The magnitude of the force exerted on the ball by the racket as a function of time is shown in the figure above. What is the speed of the ball after the collision with the racket?

30 m/s

Two blocks are connected to identical ideal springs and are oscillating on a horizontal frictionless surface. Block A has mass m, and its motion is represented by the graph of position as a function of time shown above on the left. Block B's motion is represented above on the right. Which of the following statements comparing block B to block A is correct?

Because block B has more mass, its acceleration is smaller than that of block A at any given displacement from the equilibrium position.

Block A and block B move toward each other on a level frictionless track. Block A has mass m and velocity +v . Block B has mass 2m and velocity -v . The blocks collide, and during the collision the magnitude of the net force exerted on block A is F. What is the magnitude of the net force exerted on block B, and why does it have that value?

F, because the net force is equal to the mutual contact force between the blocks.

Which of the following expressions correctly relates the magnitudes Ff and FT ?

FT < Ff < 2 FT

Two wave pulses are created simultaneously at opposite ends of a string and move toward the center of the string, as shown in the top figure above. Both pulses have the same width. The labeled figures show possible shapes of the string at different moments in time. Which of the following indicates a correct time order for the shape of the string as the pulses move along the string, come together, and move apart?

Figure X, Figure W, Figure Y

Tiny drops of oil that have different amounts of electric charge produced by a random process are sprayed into a region between a positively and a negatively charged plate. The charge on each drop is determined by analyzing the effect of the electric force on the drop's motion. Two graphs of the number of drops as a function of the charge on each drop, where e is the charge of an electron, are shown above. Which graph shows the most likely result after repeating the experiment many times, and why?

Graph 1, because it shows that within experimental error charge only exists in multiples of e

A student is asked to determine the work done on a block of wood when the block is pulled horizontally using an attached string. The student is supplied with a spring scale, a stopwatch, and a meterstick. Which of the following graphical analysis techniques will allow the student to determine the work done on the block by the string?

Graphing the force as a function of distance and calculating the area under the curve

The pendulum shown in the figure above reaches a maximum height h above the equilibrium position as it oscillates. Assuming friction and air resistance are negligible, which of the following is true about the total energy of the Earth-pendulum system as the pendulum oscillates?

It is constant throughout the pendulum's motion.

An ice-skater is moving at a constant velocity across an icy pond. The skater throws a snowball directly ahead. Which of the following correctly describes the velocity of the center of mass of the skater-snowball system immediately after the snowball is thrown? Assume friction and air resistance are negligible.

It is equal to the original velocity of the skater

Some bicycle brakes work by pressing rubber pads against the rim of the wheel. To test newly designed brakes, bicycle engineers mount a wheel of known rotational inertia on a low-friction axle, as shown above. The engineers spin the wheel with known initial angular speed and then apply the brakes with a constant force. Which of the following procedures would enable the engineers to find the torque exerted by the brakes on the wheel? Select two answers.

Measuring how much time the wheel takes to come to rest Measuring how many rotations the wheel completes while coming to rest

If the block is at rest on section 1 of the incline, what is the magnitude of the force of static friction exerted on the block by the incline?

Mgsinθ

The figure above shows a uniform beam of length L and mass M that hangs horizontally and is attached to a vertical wall. A block of mass M is suspended from the far end of the beam by a cable. A support cable runs from the wall to the outer edge of the beam. Both cables are of negligible mass. The wall exerts a force FW on the left end of the beam. For which of the following actions is the magnitude of the vertical component of FW smallest?

Moving both the support cable and the block to the center of the beam

The above table shows the potential difference and current for each circuit element in a circuit consisting of a battery and three resistors. Which of the following diagrams could represent the circuit?

R1 in series with R2 and R3 in parralel

The magnitude of the gravitational field on the surface of a particular planet is 2g. The planet's mass is half the mass of Earth. What is the planet's radius in terms of the radius RE of Earth?

RE/2

Mars moves in an elliptical orbit around the Sun, and the mass of Mars is much less than the mass of the Sun. At the instant shown above, Mars is getting farther away from the Sun. How does this affect the potential energy of the Mars-Sun system and the magnitude of Mars's angular momentum with respect to the Sun?

System potential energy - increases Mar's angular momentum - remains the same

The

The acceleration is directed downward with magnitude equal to g because the system is a projectile.

What additional measurement is needed to determine the speed of the wave on the string?

The distance between the wall and the block

The figure above shows a string held taut between a post and an oscillator that vibrates the end of the string. In an experiment, the oscillator is adjusted to find many frequencies that will create a standing wave, one of which is shown. The number of nodes in each standing wave is counted. Which of the following quantities must also be measured to determine the speed of traveling waves on the string? Select two answers.

The length of the string The frequencies of the standing wave patterns

An object starts from rest and slides with negligible friction down an air track tipped at an angle q from the horizontal. A student records values of the object's position along the track at various times. The value of q can best be determined from which of the following?

The slope of a graph of position as a function of the square of time

A guitar string of length L can vibrate with three antinodes, as shown above. The straight dashed line shows the equilibrium position of the string. The wave pattern is most likely formed by the superposition of which of the following pulses or waves?

Two periodic waves of wavelength 2L/3, one moving to the left and one moving to the right

A stone disk is sliding on frictionless ice to the west with speed v, as shown in the figure above. As the disk slides by, a child uses a rubber mallet to hit the disk at point X, exerting a force directly toward the center of the disk. The child hits point X every half second for about 10 s, changing the trajectory of the disk but not causing it to rotate. Which of the following most closely approximates the path of the disk while the child is hitting it?

a parabolic path

A small object with positive charge Q is fixed in place. A small bead with positive charge q is released from rest from the position shown above. In the absence of forces other than the electric force, which of the following graphs best represents the bead's acceleration as a function of its distance from the fixed object?

exponential curve

26. Using a force probe, a student generates the graph above of the force exerted on a small wagon as a function of time. The wagon starts from rest and rolls with negligible friction in the axles. Which of the following graphs best represents the wagon's momentum as a function of time?

parabolic curve upwards

A solid metal bar is at rest on a horizontal frictionless surface. It is free to rotate about a vertical axis at the left end. The figures below show forces of different magnitudes that are exerted on the bar at different locations. In which case does the bar's angular speed about the axis increase at the fastest rate?

the bar with the F at the end upwards

A speaker is at rest at the side of a straight road. The speaker produces a steady sound of constant frequency. A student is standing still near the speaker. Two vehicles are driven down the road: a truck approaching the speaker and a car moving away from the speaker. If the sound is represented by wave fronts, the student and the vehicle drivers each observe a different amount of time between successive wave fronts: ts for the student, tt for the truck driver, and tc for the car driver. Which of the following correctly ranks the times?

tt < ts < tc

A ball attached to a light string swings in a counterclockwise vertical circle, as shown above. Which of the following arrows represent one of the forces exerted on the ball at the moment it passes through point P ? Select two answers.

↓ ←

The data in the table below were recorded during an experiment in which two carts on a frictionless one-dimensional track collide head-on. What are the values of the magnitude of the change in momentum ∆p2 of cart 2 and the magnitude of its average acceleration a2 during the collision? Cart 1 Cart 2 Mass 5 kg 1 kg Average Force 15 N 15 N Change in Momentum 0.3 kg×m/s ∆p2 Average Acceleration 3 m/s2 a2

∆p2 a2 0.3 kg×m/s 15 m/s²

Which of the following correctly ranks the displacement ∆x for the three segments of the object's motion?

∆x3 > ∆x1 > ∆x 1> 0