There is no change in the motion of a body unless a resultant force is acting upon it.
There is no change in the motion of a body unless a resultant force is acting upon it.
除非有一合力作用于物体上，否则物体的方向是不会发生变化的。
There is no change in the motion of a body unless a resultant force is acting upon it.
除非有一合力作用于物体上，否则物体的方向是不会发生变化的。