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NEET2014PhysicsRotational MotionActual

A child is standing with folded hands at the centre of a 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 doubled. The kinetic energy of the system now is

Options

  1. A2 K
  2. BK 2
  3. CK 4
  4. D4 K

Correct answer

B. K 2

Step-by-step solution

According to the principle of conservation of angular momentum, I = constant As I is doubled, becomes half Now K.E. of rotation, K= 1 2 I ^2 Since I is doubled and is halved, K.E. will become half i.e. K 2 .

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