It should be noted: (1)An important property of all bodies- Inertia, the tendency(趋势) of bodies to maintain their original(原来的) state of motion. The force,not being the cause of motion of body, is the cause of change of motion of a body. D⑴ An important property of all bodies — Inertia, the tendency（趋势） of bodies to maintain their original（原来的） state of motion. The force, not being the cause of motion of body, , is the cause of change of motion of a body. It should be noted: