Q 7.23    A man stands on a rotating platform, with his arms stretched horizontally holding a
              5kg  weight in each hand. The angular speed of the platform is 30 revolutions per
              minute. The man then brings his arms close to his body with the distance of each
              weight from the axis changing from 90 cm to 20 cm. The moment of inertia of the
              man together with the platform may be taken to be constant and equal to 7.6 kg m^{2}.

              (b) Is kinetic energy conserved in the process? If not, from where does the change come about?

Answers (1)

No, the kinetic is not constant. The kinetic energy increases with decrease in moment of inertia. The work done by man in folding and stretching hands is responsible for this result. 

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