牛顿第三定律是牛顿第二定律的一个必要的重要补充 ,它揭示了力是物体间相互作用的性质 ,从而扩大了牛顿第二定律的适用范围 ,由单个质点扩展到多个质点。分析作用力和反作用力的作用效果、平衡力与作用力和反作用力的区别 ,是力学的一个难点。1　提出问题 ,让学生设计实验教学 Newton’s third law is a necessary and important supplement to Newton’s second law. It reveals that force is the nature of the interaction between objects, which expands the scope of Newton’s second law and extends from a single particle to multiple particles. It is a difficult point for mechanics to analyze the effects of force and reaction force, the balance force and the difference between force and reaction force. 1 Ask questions to allow students to design experimental teaching