A ballet dancer of mass 80 kg and a wingspan of 1m is executing a spin. She then folds her arms and brings them to within 20cm from the central axis of her body. If she was initially making 3 rotations per second, how many does she make now?
Correct answer: A. 75
- A. 75
- B. 8/3
- C. 12
- D. 6
Explanation
By law of conservation of momenrum;Iiwi = Ifwf1/2 mr12 wi = 1/2 mr22 wfr12 wi = r22 wf12 *3 = 0.22 wf3 = 0.04 wfwf = 75 revolutions per second.
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