来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  to find out what's in and what's not in.
  就能知道哪里重要哪里不重要了
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  If you don't do that,
  但是如果你不来
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  there's a danger you will learn something you don't have to,
  你就有可能学到一些不重要的知识
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  and we don't want that.
  我们当然不希望这样
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  Okay, so that's why you come to class.
  没错 这就是你们要来上课的原因
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  Second thing, most important thing for doing well in physics,
  接下来 学好物理最重要的就是
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  is to do the homework.
  完成作业
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  The 20% given to the homework
  作业的权重虽然只有20%
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  is not a real measure of how important it is.
  但这个数字是无法真正衡量其重要性的
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  Homework is when you really
  作业能让你真正弄清楚
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  figure out how much you know and don't know.
  自己对知识的掌握程度
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  If you watch me do the thing on the blackboard,
  如果你只看我在黑板上的推导