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AIIMS 2014
Exam
AIIMS
Year
2014
Subject
Physics
Chapter
Rotational Motion

AIIMS 2014 · Physics · Rotational Motion

A child is standing with folded hands at the centre of a platform...

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 KK. 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. A2K2 K
  2. BK2\frac{K}{2}
  3. CK4\frac{K}{4}
  4. D4K4 K

Correct answer

B. K2\frac{K}{2}

Step-by-step solution

According to the principle of conservation of angular momentum, Iω=I \omega= constant As II is doubled, ω\omega becomes half Now K.E. of rotation, K=12Iω2K=\frac{1}{2} I \omega^2 Since II is doubled and ω\omega is halved, K.E. will become half i.e. K2\frac{K}{2}.
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