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Sahay Sir > Question Answers > NCERT Exemplar Class 11 > Physics > Chapter 6 - System of Particles and Rotational Motion > A man stands on a rotating platform, with his arms stretched horizontal 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 90cm to 20cm. moment of inertia of the man together with the platform may be taken to be constant and equal t 7.6kgm2. (a) What is the his new angular speed ? (Neglect friction.) (b) Is kinetic energy conserved in the process ? If not, from where does the change come about ?

A man stands on a rotating platform, with his arms stretched horizontal 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 90cm to 20cm. moment of inertia of the man together with the platform may be taken to be constant and equal t 7.6kgm2. (a) What is the his new angular speed ? (Neglect friction.) (b) Is kinetic energy conserved in the process ? If not, from where does the change come about ?

A man stands on a rotating platform an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice applied torque is needed to counter frictional torque). Assume that the engine is 100% efficient. To maintain a rotor at a uniform angular speed of 200 rad s^−1