A man stands on a rotating platform, with his arms stretched horizontally holding a 5 kg 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 90cm to 20cm. The moment of inertia of the man together with the platform may be taken to be constant and equal to 7.6 kg m2. (a) Moment of inertia of the man-platform system = 7.6 kg m2 Kinetic energy is not conserved in the given process. But, the kinetic energy increases as there is a decrease in the moment of inertia. The additional kinetic energy comes from the work done by the man to fold his hands toward himself. |