作用力和反作用力与平衡力都是大小相等、方向相反,作用在同一条直线上.那么它们做功是否都是一个做正功.一个做负功.且总功为零呢?由功的定义式W=Fs(s为在F方向上的位移)可知,一对平衡力作用在同一个物体上,s互为相反数,总功为零:作用力和反作用力作用在不同物体上.s的关系不确定,总功不一定为零.下面就可能的情况举例说明. Force and reaction force and balance force are equal in magnitude and opposite in direction, acting on the same line. Then do they work is a positive work. One does negative work. And the total work is zero? The definition of work The formula W=Fs (s is the displacement in the F direction) shows that a pair of balancing forces act on the same object, s are opposite numbers, and the total work is zero: the acting force and reaction force act on different objects. The relationship is not certain, and the total work is not necessarily zero. Here is an example of possible situations.