A man stands on a frictionless platform that is rotating with an angular speed of 2.3 rad/s; his arms are outstretched and he holds a weight in each hand. With his hands in this position the rotational inertial of the system of man, weights, and platform is 6.8 kg*m^2.
a) If by moving the weights the man decreases the rotational inertial of the system to 4.3 kg*m^2, what is the resulting angular speed of the platform?
b) What is the change of the kinetic energy when the man moves his arms?