Newton's First Law of motion: Any object will keep its state of movement when it is left along. V =const (F=0)》 Inertia(惯性)：the property to keep one's state of movement Mass(质量)：the measure of the inertia of a body Newton’s First Law of motion: Any object will keep its state of movement when it is left along. v  const （F  0）   Inertia(惯性） ：the property to keep one’s state of movement Mass（质量）: the measure of the inertia of a body