A ballet dancer, dancing on smooth floor, is spinning about a vertical axis

A ballet dancer, dancing on smooth floor, is spinning about a vertical axis with her arms folded with an angular velocity of 20 radian/sec. When she stretches her arms fully, the spinning speed decreases to 10 radian/sec. If l is the initial moment of inertia of the dancer, the new moment of inertia is

Options

(a) 2I
(b) 3I
(c) I/2
(d) I/3

Correct Answer:

2I

Explanation:

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  • Since MI is inversely proportional to angular velocity. then if angular velocity=20 rad/sec. Gets half to 10 rad /sec .therfore moment of inertia will get doubled. Therefore correct anwers is 2l

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