AP Physics

A horizontal wheel with an initial angular velocity of ω0 spins with a constant angular acceleration α. After a time t, the wheel has reached a final angular velocity of ω. Which of the following is a correct expression for the angular displacement Δθ of the wheel during this time interval?

• ωt

• 1/2αt^2

• ω^2 - ω20

  /

  2α

• ω0+αt

An ant is standing on a fan blade of radius R at a distance of R/2 from the axis of rotation, as shown. The fan starts at rest and then begins spinning counterclockwise. The angular speed of the fan increases at a constant rate over a time t, until the fan reaches a final angular speed ωf. What is the average tangential acceleration of the ant over this time interval?

Responses

• rwf

  /

  t

• Rwf

  /

  2t

• wf/Rt

• wf/2Rt

Tags

NGSS.HS-PS2-1

Two spheres, with masses 2.0kg and 3.0kg, are mounted on a 3.0m long rod of negligible mass at the locations shown in the figure. The rotational inertia of the spheres-rod system about the left end of the rod is most nearly

Responses

• 1.3kg * m^2

• 5 kg * m^2

• 13kg * m^2

• 19kg * m^2

The figure shows a disk, with radius 0.50m, connected to a motor by an axle. A brake touches the edge of the disk and exerts a constant force on the disk. The motor delivers a torque of magnitude 150N·m to the disk and the disk rotates at a constant angular speed of 50rad/s. What is the magnitude of the torque exerted by the brake on the disk?

• 300 Nm

• 150 Nm

• 75 Nm

• 0 Nm

A pulley with radius R, mass m, and rotational inertia I is free to rotate about an axle at the pulley’s center. Two blocks are attached by a string of negligible mass that passes over the pulley, as shown. The tension T2 in the part of the string attached to Block 2 is greater than the tension T1 in the part of the string attached to Block 1. The string does not slip on the pulley and frictional forces on the axle are negligible. Which of the following is a correct expression for the angular acceleration of the pulley?

• (T2-T1)R/I

• (T2+T1)R/I

• (T2-T1+mg)R/I

• (T2+T1+mg)R/I

Tags

NGSS.HS-PS2-1

Three fans undergo different angular displacements over different time intervals. The angular displacement and elapsed time for each fan is described in the table. Which of the following correctly compares the average angular speed ω of the fans?

• w2>w1>w3

• w2>w3>w1

• w3>w1>w2

• w3>w2>w1

Point A is on Earth’s equator at a distance RE=6.38×10^6m from the axis of Earth’s rotation, as shown. Point B is at a latitude of 53° north of the equator at a distance r from Earth’s axis of rotation. The total distance traveled by Point B during one complete rotation of Earth is most nearly

Responses

• 4* 10^7

• 2.4* 10^7

• 2** 10^7

• 1.2* 10^7

A uniform meterstick has three labeled points at the locations shown in the figure. The rotational inertia of the meterstick about its center is 1/12ML2 where M is the mass and L is the length of the meterstick, respectively. Which of the following correctly compares IA, IB, and IC, the rotational inertia of the meterstick about points A, B, and C, respectively?

• IA>(IB=IC)

• (IB=IC)>IA

• IA>IB>IC

• IC>IB>IA

A sign of mass m hangs from the right end of a horizontal rod, also of mass m that is pivoted about an axis at its left end. A vertical rope is connected to the right end of the rod, as shown in Figure 1, and the rope exerts a torque of magnitude τr1 on the rod to keep the rod and sign in equilibrium. In Figure 2, the rope and the sign are moved to the midpoint of the rod and the system is again in equilibrium. The magnitude of the torque exerted by the rope is τr2. Which of the following correctly relates τr2 to τr1 ?

• Tr2 = Tr1/2

• Tr2 = Tr1

• Tr2 = 2Tr1/3

• Tr2 = 2Tr1

Two thin rings are spinning counterclockwise about an axis perpendicular to the rings’ centers. Ring 1 has mass m and radius r, while Ring 2 has mass m and radius 4r. Identical counterclockwise torques are exerted on each ring. The rotational inertia of a ring of mass M and radius R is Iring=MR2. Which of the following correctly relates α1 and α2, the angular acceleration of Ring 1 and Ring 2, respectively?

• α1 = α2/4

• α1 = α2

• α1= 4α2

• α1 = 16α2