For a solid, extended object, it does, in fact, provide us with the precise form that the law of inertia must take: in the absence of external forces, the center of mass will just move on a straight l...For a solid, extended object, it does, in fact, provide us with the precise form that the law of inertia must take: in the absence of external forces, the center of mass will just move on a straight line with constant velocity, whereas the object itself may be moving in any way that does not affect the center of mass trajectory.
