Rotating Systems: Energy & Momentum
A spinning ice skater pulls their arms inward during a spin. Assuming there is negligible external torque, what happens to the skater's angular momentum?...
Angular momentum increases.
Angular momentum decreases.
Angular momentum remains constant.
Angular momentum becomes zero.
A rotating object has its moment of inertia reduced to one-third of its original value. If no external torque acts on the object, what is the new angular velocity in terms of its original angular velocity ?...
3\omega_0
9\omega_0
A system consists of a rotating platform and a person standing at the center. The person then walks to the edge of the platform. During this process, both the moment of inertia of the system changes and there is friction at the axis of rota...
The final angular velocity can only be determined by knowing the exact values of the frictional torque and change in moment of inertia.
The final angular velocity will always be greater than the initial angular velocity.
The final angular velocity will always be less than the initial angular velocity.
The final angular velocity will remain the same as the initial angular velocity.
A solid disk with a moment of inertia of 2 \, kg \cdot m^2
is rotating at an angular velocity of 5 \, rad/s
. What is the magnitude of its angular momentum?...
2.5 \, kg \cdot m^2/s
7 \, kg \cdot m^2/s
10 \, kg \cdot m^2/s
20 \, kg \cdot m^2/s
Two identical disks are rotating about the same axis. Disk A has an angular momentum of and Disk B has an angular momentum of 2L
in the same direction. What is the total angular momentum of the system?...
2L
3L
4L
In a binary star system, two stars orbit each other. Star A has mass and Star B has mass . If the distance between them remains constant, and no external torques act on the system, what can be said about the total angular momentu...
The total angular momentum increases over time.
The total angular momentum decreases over time.
The total angular momentum remains constant.
The total angular momentum oscillates.
A wheel initially at rest experiences a constant external torque of 10 \, N \cdot m
for 5 \, s
. What is the magnitude of the change in angular momentum of the wheel?...
2 \, kg \cdot m^2/s
10 \, kg \cdot m^2/s
50 \, kg \cdot m^2/s
250 \, kg \cdot m^2/s

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A spinning top is subject to a frictional torque. What effect does this torque have on the angular momentum of the top?...
The angular momentum increases.
The angular momentum remains constant.
The angular momentum decreases.
The angular momentum oscillates.
A student is sitting on a rotating stool holding a spinning bicycle wheel. The student turns the bicycle wheel upside down. For the system of the student and the wheel, is angular momentum conserved?...
Yes, because the system is isolated.
No, because the wheel is changing direction.
Yes, because there are no external torques acting on the system.
No, because the moment of inertia is changing.
A rotating object collides with a stationary object, and they stick together. Which of the following is true about the angular momentum and kinetic energy of the system?...
Both angular momentum and kinetic energy are conserved.
Angular momentum is conserved, but kinetic energy is not conserved.
Kinetic energy is conserved, but angular momentum is not conserved.
Neither angular momentum nor kinetic energy is conserved.