But there's another way to do this and I'm going to give you now the simplest example of the other way, which is to draw free-body diagrams.

不过还有另外一种方法,现在我来给你们演示,另外一种方法最简单的例子,也就是隔离法的受力分析

耶鲁公开课 - 基础物理课程节选

Let's get that systematically by using free-body diagrams.

让我们系统地用隔离法来分析一下

耶鲁公开课 - 基础物理课程节选

A simple example of free body diagrams.

隔离法的一个简单例子

耶鲁公开课 - 基础物理课程节选

The free-body diagram, it says you can pick any one body that you like and apply F = ma to it, provided you identify all the forces acting on that body.

所谓隔离法,就是说你可以任意 选取一个物体,分析出它所受的所有力后,单独对其运用 F = ma 进行计算

耶鲁公开课 - 基础物理课程节选