Point masses m1 and m2, are placed at the opposite ends of a rigid rod of length L, and negligible mass. The rod is to be set rotating about an axis perpendicular to it. The position of point P on this rod through which the axis should pass so that the work required to set the rod rotating with angular velocity it minimum, is given by :
As moment of inertia is minimum about centre of mass so point P must be centre of mass.