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A ballet dancer revolved at 24 r.p.m. wi...

A ballet dancer revolved at 24 r.p.m. with her hands folded. If she stretches her hands so that her M.I. increases by 20%, then the new frequency of rotation will be

A

18 r.p.m.

B

20 r.p.m.

C

22 r.p.m.

D

24 r.p.m.

Text Solution

Verified by Experts

The correct Answer is:
B
By the principle of conservation of angular momentum,
`I_(1)omega_(1)=I_(2)omega_(2)`
`therefore I_(1).2pin_(1)=(12)/(10)I_(1).2pin_(2)`

`n_(1)=(12)/(10)n_(2)=(6)/(5)n_(2)`
`therefore n_(2)=(5)/(6)n_(1)=(5)/(6)xx(24)/(60)=(1)/(3)`
`therefore " No. fo rev/minute "=(1)/(3)xx60="20 r.p.m."`
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