A disgruntled hockey player throws a hockey stick along the ice. It rotates about its center of mass as it slides along and is eventually brought to rest by the action of friction. Its motion of rotation stops at the same moment that its center of mass comes to rest, not before and not after. Explain why.

In accordance to conservation of energy,
F_ext s = ½ Mv_cm² + ½ Iw²
Here F_ext is the external fore, s is the displacement, M is the mass, v_cm is the speed, I is the moment of inertia and w is the angular velocity.
Since there is no external force, so the left hand side of equation F_ext s will be equal to zero. Thus the kinetic energy of the center of mass of hockey stick will be to the rotational kinetic energy of the stick. Therefore the motion of rotation of hockey stick stops when velocity of its center of mass equal to zero results its center of mass comes to rest. From the above observation we conclude that, the motion of rotation of hockey stick stops at the same moment that its center of mass comes to rest.