An ice skater performs a pirouette (a fast spin) by pulling in his outstretched arms close to his body. What happens to his moment of inertia about the axis of rotation?
A) It changes, but it is impossible to tell which way.
B) It does not change.
C) It decreases.
D) It increases.

Question

Quizplus · Accepted Answer

When the ice skater pulls his arms in close to his body, his moment of inertia decreases because the distribution of his mass relative to the axis of rotation becomes more compact, leading to a faster spin due to conservation of angular momentum.

An Ice Skater Performs a Pirouette (A Fast Spin) by Pulling