摩擦力是一种被动力,其产生有一定的条件.当影响产生摩擦力的条件变化时,能引起摩擦力的大小和方向发生“突变”;而突变往往隐含在物体的运动过程中,能否正确发掘出题中所含的“突变”是解题的关键,也是考查学生素质的高低.本文就此分类浅析. Friction is a kind of motive power, and its production has certain conditions. When the conditions affecting the frictional force change, it can cause the “friction” of the magnitude and direction of the friction force; and the abrupt change is often hidden in the motion process of the object. The key to solving the problem is whether or not the “abrupt change” contained in the question can be correctly explored. It is also a measure of the quality of students.