Question

When angular momentum is conserved, rotational speed:

A. may increase but can never decrease.
B. decreases if the mass moves farther from the axis of rotation.
C. increases if the mass moves farther from the axis of rotation.
D. must be constant.

Answer 1

Rotational speed increases if the mass moves closer to the axis of rotation and decreases if it moves farther away, due to the law of conservation of angular momentum, which requires angular velocity to adjust when moment of inertia changes.

Step-by-step explanation:

Whenm angular momentum is conserved, the correct answer to the student's question is that rotational speed increases if the mass moves closer to the axis of rotation and decreases if the mass moves farther from the axis of rotation. This is a consequence of the law of conservation of angular momentum, which states that if no external torque is applied to a syste, the total angular momentum remains constant. Therefore, when the moment of inertia of a rotating object changes, its angular velocity must adjust to maintain the conservation of angular momentum. For example, when a figure skater pulls their arms in, they reduce their moment of inertia and spin faster to conserve angular momentum (a smaller I requires a larger ω for L = Iω to remain constant).