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一个摩擦力可以对物体做正功,也可以做负功,还可以不做功.做功的结果可能使物体的动能增加,也可能使物体的动能减少.而一对相互作用的摩擦力分别对两个物体做功,如果是静摩擦力,两个功的代数和一定等于零,它表明一对静摩擦力做功的结果使一部分机械能在两个物体间转移,而没有机械能和其它形式的能量的转化.如果是滑动摩擦力,这两个功的代数和一定是负值,它表明除了机械能在两个物体间转移以外,还有一部分机械能转化为内能.一般情况下用公式“Q=f·s相对”求解摩擦而产生的热量较为简便.
A friction can do positive work on the object, it can also do negative work, and it can also do no work. The result of work may increase the kinetic energy of the object, and may also reduce the kinetic energy of the object. A pair of interacting friction forces are respectively If the object is doing work, if it is static friction, the algebraic sum of the two work is equal to zero, which indicates that the result of a pair of static friction work will cause part of the mechanical energy to be transferred between the two objects without the conversion of mechanical energy and other forms of energy. Sliding friction, the algebraic sum of these two work is definitely negative. It shows that in addition to mechanical energy transfer between two objects, there is still a part of mechanical energy converted to internal energy. In general, the formula “Q=f·s relative” is used. It is more convenient to solve the heat generated by the friction.