A child stands at the centre of a turn table with his two arms outstretched. The turn table is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child, if he folds his hands back reducing the moment of inertia to (2/5) times the initial value? Assume that turntable rotates without friction.(b) Show that the child's new K.E of rotation is more than the initial K.E. of rotation. How do you account for this increase in K.E.?

Explanation

a) 100rpm, b) K.E. of rotation increases. This is because the child spends internal energy in folding back his hands.