文章较细致地分析了地面对小球底部的各个微观滑动摩擦力在无穷小时间内所做的总功，从而获得宏观滑动摩擦力作用点的元位移表达式，并指出该作用点在做功时是一个虚设的概念；通过积分得到小球的实际滑动距离，从而计算出所有滑动摩擦力所做的总功；指出小球滑动的距离加上小球滚动的距离就等于小球质心的位移，同时指出小球的滑动与滚动是同时而非交替进行的；证明了从形式上看，滑动摩擦力在小球质心的整个位移上做负功导致了小球平动动能的减少，而在反向的滚动距离上做正功，则导致了小球转动动能的增加.文章的主要目的在于揭示出地面对边滑边滚小球的滑动摩擦力做功的一些细节与机制.

This article analyzes in detail the total work done by the microscopic sliding friction forces at the bottom of the small ball in an infinitely small time, and obtains the expression of the elementary displacement of the point of action of the macroscopic sliding friction force. It is pointed out that the action point is a hypothetical concept when the work is done. The actual sliding distance of the small ball is obtained by integration, and the total work done by all sliding friction forces is calculated. It is pointed out that the distance of the small ball sliding plus the distance of the small ball rolling is equal to the displacement of the center of mass of the small ball. It is also pointed out that the sliding and rolling of the small ball are carried out simultaneously rather than alternately. It is proved that, formally, the negative work done by the sliding friction force on the entire displacement of the center of mass of the small ball leads to the decrease of the translational kinetic energy of the small ball, while the positive work done on the reverse rolling distance leads to the of increase in the rotational kinetic energy of the small ball. The main purpose of the article is to reveal the mechanisms of the work done by the sliding friction force acting on a small ball sliding and rolling on the ground.