MCQ Unit V: Rotation

A hoop of mass m and radius r rolls with constant speed on a horizontal surface without slipping. What is the hoop’s translational kinetic energy divided by its rotational kinetic energy?

• 4

• 2

• 1

• 1/2

• 1/4

A meterstick of negligible mass is placed on a fulcrum at the 0.4 m mark, with a 1 kg mass hung at the zero mark and a 0.5 kg mass hung at the 1.0 m mark. The meterstick is held horizontal and released. Immediately after release, the magnitude of the net torque on the meterstick about the fulcrum is most nearly

• 1 N.m

• 2 N.m

• 2.5 N.m

• 7 N.m

• 7.5 N.m

Tags

NGSS.MS-PS2-4

A particle of mass 2.0 kg is moving in the xy-plane at a constant speed of 0.80 m/s in the +x-direction along the line y = 4 m. As the particle travels from x = -3 m to x = +3 m, the magnitude of its angular momentum with respect to the origin is

• not constant

• 0

• 4.8 kg.m²/s

• 6.4 kg.m²/s

• 8.0 kg.m²/s

A student initially stands on a circular platform that is free to rotate without friction about its center. The student jumps off tangentially, setting the platform spinning. Quantities that are conserved for the student-platform system as the student jumps include which of the following?

I. Angular momentum

II. Linear momentum

III. Kinetic energy

• I only

• II only

• I and II only

• II and III only

• I, II and III

Tags

NGSS.HS-PS2-2

A wheel with rotational inertia 0.04 kg•m² and radius 0.02 m is turning at the rate of 10 revolutions per second when a frictional torque is applied to stop it. How much work is done by the torque in stopping the wheel?

• -0.0008 J

• -0.4 $\pi$ J

• -2 J

• -2 $\pi^2$ J

• -8 $\pi^2$ J

Tags

NGSS.HS-PS3-1

All of the following are vector quantities EXCEPT

• rotational kinetic energy

• torque

• angular momentum

• angular velocity

• centripetal acceleration

Two horizontal disks of mass M have the radii shown above. Disk A is attached to an axle of negligible mass spinning freely with angular velocity ω₀. Disk B, not attached to the axle and initially held at rest, is released and drops down onto disk A. When both disks spin together without slipping, the angular velocity ω_f of the disks is

• $\frac{1}{3}\omega_0$

• $\frac{1}{2}\omega_0$

• $\frac{2}{3}\omega_0$

• $\frac{4}{5}\omega_0$

• $\frac{2}{\sqrt{5}}\omega_0$

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A sphere starts from rest at the top of a ramp, as shown above. It rolls without slipping down the ramp. The potential energy of the sphere-Earth system is zero at the bottom of the ramp. Which of the following is true of the sphere when it reaches the bottom of the ramp?

• Its rotational kinetic energy equals the initial potential energy of the sphere-Earth system.

• Its translational kinetic energy equals the initial potential energy of the sphere-Earth system.

• Its translational kinetic energy and rotational kinetic energy are equal.

• The sum of its translational kinetic energy and rotational kinetic energy equals the initial potential energy of the sphere-Earth system.

• The sum of its translational kinetic energy and rotational kinetic energy equals the energy lost because of friction.

Tags

NGSS.HS-PS3-1

Suppose that a spherical star spinning at an initial angular velocity ω suddenly collapses to half of its original radius without any loss of mass. Assume the star has uniform density before and after the collapse. What will the angular velocity of the star be after the collapse?

• $\frac{\omega}{4}$

• $\frac{\omega}{2}$

• $\omega$

• $2\omega$

• $4\omega$

Tags

NGSS.HS-PS2-2

A uniform beam of weight W is attached to a wall by a pivot at one end and is held horizontal by a cable attached to the other end of the beam and to the wall, as shown above. T is the tension in the cable, which makes an angle θ with the beam. Which of the following is equal to T ?

• $\frac{W}{2\cos\theta}$

• $\frac{W}{2\sin\theta}$

• $\frac{W}{\cos\theta}$

• $\frac{W}{\sin\theta}$

• $W$

Tags

NGSS.HS-PS2-1