来自《耶鲁大学开放课程：基础物理 第4集 第4集》

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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
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  you're told what that angle is.
  还有这个角度
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  You are supposed to find the tension on these two ropes.
  你要求出两根绳子的张力
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  I think it's fairly simple so I won't do the details
  我觉得题目相当简单 就不写详细过程了
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  but you know what you're supposed to do.
  但你们应该知道要怎么做
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  You take these two tensions,
  把这两个拉力