Solution: A man holding a heavy object in each hand stands on a small platform that is free to rotate about a vertical axis. Initially he is standing with his arms outstretched and he and the platform are rotating with an angular velocity of 0.800 rad/s. With his arms outstretched, the moment of inertia of the system (man + platform + weights) is 4.00 kg•m2. Then he pulls the weights in close to his chest, and the moment of inertia of the system becomes 3.00 kg•m2. How much work did the man do when he pulled his arms in?

Problem

A man holding a heavy object in each hand stands on a small platform that is free to rotate about a vertical axis. Initially he is standing with his arms outstretched and he and the platform are rotating with an angular velocity of 0.800 rad/s. With his arms outstretched, the moment of inertia of the system (man + platform + weights) is 4.00 kg•m2. Then he pulls the weights in close to his chest, and the moment of inertia of the system becomes 3.00 kg•m2. How much work did the man do when he pulled his arms in?