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MHT CET202122 Sep 2021Evening ShiftPhysicsRotational MotionActual

A child is standing with folded hands at the centre of the platform rotating about its central axis. The kinetic energy of the system is ' K '. The child now stretches his arms so that the moment of inertia of the system becomes double. The kinetic energy of system now is

Options

  1. AK 2
  2. B2 ~K
  3. C4 ~K
  4. DK 4

Correct answer

A. K 2

Step-by-step solution

aligned K & = 1 2 I ^2 I ^ & =2 I aligned By law of conservation of angular momentum aligned & I ^ ^ = I & 2 I ^ = I & ^ = 2 & ~K ^ = 1 2 I ^ ^ 2 = 1 2 (2 I ) ( 2 )^2= 1 2 ( 1 2 I ^2 )= K 2 aligned

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