高中学习的摩擦力主要是静摩擦力和滑动摩擦力,教学中发现二者往往会因物理情景的变化而发生突变,解答时要求学生具备动态分析问题的能力,对学生能力要求较高,因此这类问题是学生普遍感到困难的地方.本文就此问题进行归类,以帮助学生得以突破.1静静“突变”物体在摩擦力和其他力作用下处于相对静止状态,当其他力的合力变化时,若物体仍处于相对静止状态,静摩擦力会发生突变.图1例1.一木块放在水平桌面上,在 High school learning friction is mainly static friction and sliding friction, teaching found that both often due to changes in the physical scene of the mutation, the answer requires students to have the ability to dynamically analyze the problem, the higher the ability of students, so this Class problems are generally difficult place for students.This paper classifies this problem to help students to make breakthroughs.1 Quiet “Mutation ” objects are in relative quiescence under the action of friction and other forces, and when the force of other forces Changes, if the object is still relatively at rest, static friction mutations will occur Figure 1 Example 1. A wooden block on a horizontal table, in the