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JEE Main20203 Sep 2020Morning ShiftPhysicsRotational MotionActual

A person of 80   kg mass is standing on the rim of a circular platform of mass 200   kg rotating about its axis at 5 revolutions per minute (rpm). The person now starts moving towards the centre of the platform. What will be the rotational speed (in rpm ) of the platform when the person reaches its centre....

Correct answer

9

Step-by-step solution

Applying conservation of angular momentum, mR 2 + MR 2 2 ω = MR 2 2 ω ' 80 + 200 2 × 5 = 200 2 ω ' ω ' = 9 rev / sec .

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