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 0.600 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 angular velocity of the rotating system becomes 1.80 rad/s. What is the moment of inertia of the system after he has pulled his arms in?

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 0.600 rad/s. With his arms outstretched, the moment of inertia of the system (man + platform + weights) is 4.00 kg•m^{2}. Then he pulls the weights in close to his chest and the angular velocity of the rotating system becomes 1.80 rad/s. What is the moment of inertia of the system after he has pulled his arms in?