AP Physics 1 - Unit 6

• 8 kg · m^2/s

• 12 kg · m^2/s

• 16 kg · m^2/s

• 20 kg · m^2/s

The graph shows the net torque exerted on a rigid object as a function of time. Which of the following claims about the angular impulse delivered to the object during the interval shown in the graph is true?

• The angular impulse is zero.

• The angular impulse is less than zero.

• The angular impulse is greater than zero.

• The angular impulse could be greater than or less than zero depending on the initial direction of rotation.

Two forces of equal magnitude are exerted at separate times to a board that is initially at rest and free to rotate about an axis at one end of the board, as shown in the figures. In Figure 1, a force of magnitude F is exerted perpendicular to the board at the center of the board for a time 2t, after which the board has a final angular momentum about the axis of magnitude L1. In Figure 2, the board is returned to rest at its initial position and a force of magnitude F is exerted at a constant angle to the board of 60° at the end of the board for time t, after which the board has a final angular momentum about the axis of magnitude L2. Which of the following is equal to the ratio L2 : L1?

• (A) 1 : 1

• (B) 1 : 2

• (D) 1 : 4

Tags

NGSS.HS-PS2-1

The diagram shows an amusement park ride that consists of a car of mass m connected to a motor by a rigid arm of length R. The motor spins the arm and the car moves in a vertical circle. In Figure 1, the car is at the bottom of the circle with a tangential velocity of magnitude v1. In Figure 2, the car has moved clockwise along the circle through an angle θ, and has tangential velocity of magnitude v2, where v2 > v1. Which of the following is equal to the change in angular momentum of the car about the rotation axis between Figure 1 and Figure 2?

• mR(v2 − v1)

• mgR(1 − cos θ)

• mv2Rsin θ

Tags

NGSS.HS-PS2-1

A disk slides with constant velocity on a horizontal surface, as shown in the top-view figure. Friction forces between the disk and the surface are negligible. Which of the following statements correctly describes the angular momentum of the disk relative to Point P?

• The angular momentum is constant and zero.

• The angular momentum is constant and greater than zero.

• The angular momentum decreases.

• The angular momentum increases.

In an experiment, a puck slides toward the end of a rod that is free to rotate on a horizontal surface about a pivot at its left end, as shown in the top view figure. In each trial, the puck slides with constant speed v but the angle θ between the velocity vector and the rod is varied. The angular momentum L of the puck about the pivot immediately before the puck reaches the rod is calculated. Which of the following graphs could show L as a function of θ?

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A horizontal platform is initially rotating about a vertical axis as shown in Figure 1. A stationary disk is dropped directly onto the center of the platform. A short time later, the disk and platform rotate together without slipping, as shown in Figure 2. How does the angular momentum of only the platform change, if at all, after the disk drops? What is a justification for your answer?

• The angular momentum of the platform decreases. The top disk exerts a torque on the platform.

• The angular momentum of the platform decreases. The potential energy of the platform-disk-Earth system decreases when the disk drops.

• The angular momentum of the platform stays the same. Angular momentum is a conserved quantity.

• The angular momentum of the platform stays the same. The torques that the disk and platform exert on each other are equal in magnitude but opposite in direction.

An object of mass 2 kg is moving to the left with a constant speed of 3 m/s along the dashed line y = 3 m. At the instant shown in the figure, the object is at coordinates (4 m, 3 m). Which of the following is most nearly the magnitude of the angular momentum of the object with respect to the origin?

• Zero

• 18 kg·m/s

• 24 kg·m/s

• 30 kg·m/s

A rod is attached to a pivot at one end and rests on a horizontal surface, as shown. Frictional forces are negligible. In Figure 1, a puck is launched perpendicularly to the rod and makes contact at the far edge of the rod while traveling with a speed v. The angular momentum of the puck with respect to the pivot immediately before impact is L₁. In Figure 2, the same puck is launched again at the rod but at an angle of 30° to the rod. The puck makes contact at the center of the rod while traveling with speed v. The angular momentum of the puck with respect to the pivot immediately before impact is L₂. Which of the following correctly represents L₂ in terms of L₁?

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A student with mass m runs and jumps onto the outer edge of a stationary horizontal platform that is free to rotate about an axis at the center of the platform. The platform has mass M, radius R, and rotational inertia 1/2 MR². Immediately before landing on the platform the student has horizontal speed v directed tangentially to the outer edge of the platform. Which of the following is equal to the angular momentum of the student about the platform’s axis immediately before landing on the platform?

• 1/2 Rmv

• Rmv

• 1/2 RMv

• RMv

Tags

NGSS.HS-PS2-2