Okay, so with that, if you write the right forces, you will be just fine.

本着这个原则如果你受力分析画对了,那就功德圆满了

耶鲁公开课 - 基础物理课程节选

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

Maybe you should complete the force acting on this one.

也许该由你们来完成它的受力分析

耶鲁公开课 - 基础物理课程节选