❓ why
Why do ice skaters spin faster when they pull in their arms?
Quick Answer
They spin faster because pulling in their arms reduces their moment of inertia. To conserve angular momentum, the rotation rate increases.
The Full Story
Angular momentum is conserved when outside torques are small, so if a skater changes body shape, the spin speed must adjust. With arms extended, more mass is farther from the rotation axis, giving a larger moment of inertia and slower spin. When the skater pulls the arms inward, the moment of inertia drops, so the spin speeds up. This is the same physics behind collapsing stars spinning faster as they shrink.
Key Facts
1.Angular momentum is conserved when external torque is small
2.Pulling in the arms lowers moment of inertia
3.This principle also appears in rotating stars and collapsing clouds
YouTube Angle
Suggested video title for this topic:
"Why do skaters spin faster when they tuck in?"
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