What conserved physical quantity explains why an ice skater spins faster when drawing their outstretched arms close to their body?
Answer and explanation
Correct answer: A. Angular momentum
- Step 1: In the absence of external net torque, the total angular momentum of the system is strictly conserved: .
- Step 2: Drawing arms inward decreases the moment of inertia , which forces rotational velocity to increase proportionally.
Answer
Angular momentum.
Why not the others: 'Linear momentum' applies to straight-line motion; 'Mechanical energy' is not conserved because the skater does internal biological muscular work pulling arms inward; 'Gravitational potential' remains constant at ground level.
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