来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  Now, there is one other celebrated formula that goes with this.
  与这种情况对应的还有一个著名的公式
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  I'm going to find that, then I'll give you an example.
  我会推导出来 之后再给你们举一个例子
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  Now, I'm fully aware that
  我很清楚
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  this is not the flashiest example in physics,
  这个并不是物理学中最经典的例子
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  but I'm not worried about that right now.
  但是这并是我现在的担心
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  You'll see enough things that will confound you,
  你将会发现很多物理问题会让你困扰
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  but right now I want to demonstrate a simple paradigm of
  而眼下我会举一个例子来阐述
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  what it means to know the present
  什么叫了解现在
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  and what it means to say this is what the future behavior will be.
  什么又叫预测未来
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  We want to do that in the simplest context,
  我们想举一个最简单的情景
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  then we can make the example more and more complicated,
  随后我们可以再看一下更复杂的情况
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  but the phenomenon will be the same.
  但是万变不离其宗