Conservation Of Angular Momentum
A figure skater with arms extended has a moment of inertia of 4 kg·m² and rotates at 2 rad/s. When she pulls her arms in, her moment of inertia becomes 2 kg·m². What is her new angular velocity?
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About This Question
- Subject
- physics
- Chapter
- rotational motion
- Topic
- conservation of angular momentum
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
4 rad/s
- Conservation Law: If net external torque is zero, L=Iω remains constant.
- Equation: I1ω1=I2ω2.
- Application:
- 4×2=2×ω2.
- 8=2ω2.
- Result: ω2=4 rad/s.
- Concept: By pulling arms in, the mass is distributed closer to the axis, reducing I and forcing ω to increase to keep L conserved.
This medium difficulty physics question is from the chapter rotational motion, covering the topic of conservation of angular momentum. It appeared in the 2025 exam.
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