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A boy stands over the centre of a horizontal platform which is rotating freely with a speed of 2 revolutions/s about a vertical axis through the centre of the platform and straight up through the boy. He holds 2 kg masses in each of his hands close to his body. The. combined moment of inertia of the system is 1 kg×metre2. The boy now stretches his arms so as to hold the masses far from his body. In this situation, the moment of inertia of the system increases to 2kg×metre2. The kinetic energy of the system in the latter case as compared with that in the previous case will

a
Remain unchanged
b
Decrease
c
Increase
d
Remain uncertarn

detailed solution

Correct option is B

I is doubled. ω is halvedRotational K.E =12lω2Clearly, rotational KE is decreased.

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