Right now at this point in our course, whenever you have a problem where there is some body and someone says, "Write all the forces on it", what you have to do is very simple.
现在在我们这个课程里,如果你遇到一道题目,题目给了你一个物体,并要求你,"写出该物体所受的所有力",你要做的其实很简单
So, you probably don't want to pick any point down here, because you're not getting anything by picking a point down there because you could have a better point by just moving it up here.
你不会选择这里以下的任意一点,因为你的回报不是最优的,上面这一点会使你有更好的回报。
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