alleryAn ice skater spinning with arms outstretched pulls her arms in. Her angular speed:
ADecreases
BBecomes zero
CStays the same
DIncreases
Answer & Solution
Correct answer: D. Increases
1. External torque on the skater about the spin axis is negligible.
2. Angular momentum L = I ω is conserved.
3. Pulling arms in REDUCES I (mass moves closer to the spin axis).
4. Therefore ω must INCREASE to keep L constant.
5. KE = ½ I ω² actually INCREASES — work done by the skater's muscles.
_Source: syllabus Physics Ch 6 §6.10 (illustrative example)_
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