杠杆示意图是实体杠杆的抽象。从常见的工具、设备、机器中简单地抽象出杠杆模型,不但是画杠杆示意图的基础,是解决杠杆类问题的关键,而且也是初中学生最感困难的地方。我们在教学时,采用以下方法可使学生比较容易地掌握杠杆的基本画法,还可以在训练学生作图能力的同时逐步发展学生抽象的能力。一、辨认杠杆放正位置初中物理教材中将杠杆定义为“一根在力的作用下可以绕固定点转动的硬棒”。实际上,“硬棒”并不局限于棒,凡是在力的作用下绕固定轴转动的坚硬物体都可看作杠 The lever diagram is an abstraction of the physical lever. The lever model is simply abstracted from common tools, equipment, and machines. It is not only the basis for drawing the lever diagram, but also the key to solving the problem of levers. It is also the most difficult place for junior high school students. When we teach, we can use the following methods to make it easier for students to master the basic drawing method of leverage. It is also possible to gradually develop students’ abstract abilities while training students’ drawing ability. First, identify the leverage to position the junior middle school physics textbook defines the lever as “a hard rod that can rotate around a fixed point under the force of force.” In fact, “hard sticks” are not limited to sticks. Any hard object that rotates around a fixed axis under force can be regarded as a bar.