When a spinning ice skater pulls in his arms, he spins faster because .
A)there exists an unbalanced reaction force
B)there is less friction with the ice
C)there is less friction with the air
D)his angular momentum must be conserved, so reducing his radius must increase his speed of rotation

Question

Quizplus · Accepted Answer

According to the conservation of angular momentum, the product of rotational inertia and rotational velocity of a spinning object remains constant as long as no external torque is acting on it. When the ice skater pulls in his arms, he reduces his rotational inertia, meaning he must compensate by increasing his rotational velocity to maintain his angular momentum. This results in him spinning faster. Therefore, reducing the radius is the reason for the increased speed of rotation, as stated in choice D.

When a Spinning Ice Skater Pulls in His Arms, He