An ice skater doing a spin pulls in her arms, decreasing her moment of inertia by a factor of two. How does her angular speed changes?
A) It is reduced by a factor of two.
B) It is reduced by a factor of four.
C) It increases by a factor of two.
D) It increases by a factor of four.
E) It doesn't change.

Question

Quizplus · Accepted Answer

According to conservation of angular momentum, the product of moment of inertia and angular velocity is constant. When the ice skater reduces her moment of inertia by a factor of two, her angular velocity has to increase by a factor of two to keep the product constant. Therefore, her angular speed increases by a factor of two.

An Ice Skater Doing a Spin Pulls in Her Arms