来自《耶鲁大学开放课程：基础物理 第4集 第4集》

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  But that's a very--
  但那是个非常...
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  that's got some interesting angles you should think about.
  你应该思考一下其中某些有趣的角度
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  Okay, so now I'm going to do physics
  好 现在继续讲物理
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  that basically involves rotational motion.
  涉及一些很基础的旋转的问题
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  But let me do one Mickey-Mouse problem,
  让我们做一道简单的题目
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  and let it go, because I assigned it to you.
  剩下的就不做了 因为这是给你们的任务
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  The typical problem is:
  这个典型问题就是
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  there's a tree here,
  这儿有一棵树
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  there's a tree here,
  这儿也有一棵树
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  and that is--there are two ropes
  在这儿 有两根绳子
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  and there's a backpack hanging here with some weight.
  有一定重量的东西挂在这里
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  You are told what that angle is;
  已知这个角度