What impact does pulling in arms have on an ice skater’s spin?

When an ice skater pulls their arms in toward their body while spinning, this action has a significant effect on their angular velocity due to the principles of conservation of angular momentum. Angular momentum is defined as the product of an object’s moment of inertia and its angular velocity.

When the skater draws their arms in, they reduce their moment of inertia, which is a measure of how mass is distributed with respect to the axis of rotation. According to the conservation of angular momentum, if no external torque acts on the system, the total angular momentum must remain constant. Therefore, if the moment of inertia decreases while keeping angular momentum constant, the angular velocity must increase to compensate.

Thus, by pulling in their arms, the skater effectively increases their spin speed or angular velocity. This is why, as skaters perform this maneuver, they are able to spin faster.