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MHT CET 2025 (26 Apr, Shift 2) · Angular Momentum & its Conservation

Angular Momentum & its Conservation question from MHT CET 2025 (26 Apr, Shift 2)

Q18MHT CET 2025 · 26 APR · SHIFT 2Medium

Angular Momentum & its Conservation

A man standing on a turn-table is rotating at a certain angular frequency with his arms outstretched. He suddenly folds his arms. If his moment of inertia with folded arms is $75\%$ of that with outstretched arms, then his rotational kinetic energy will

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Answer: (a)

No external torque, so $L$ is constant and $K=\frac{L^2}{2I}\propto\frac1I$ .
$I'=0.75I\Rightarrow K'=\frac{K}{0.75}=\frac43K$
Increase $=\frac13=33.3\%$
So the answer is (a) increase by 33.3%.

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