来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  by seeing how fast the particle is moving
  来判断当前的时间
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  because you know it started with some speed.
  因为你知道它的初速度
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  It's gaining speed at some rate a.
  速度的增长速率为a
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  So, if the speed was so and so now,
  所以 如果速度在过去和现在都是这样
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  then the time had to be this.
  那时间就是这个
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  So time can be indirectly inferred from these quantities.
  时间可以由这些量间接推出
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  Then you take that formula here
  你再拿这个式子
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  and you put it here,
  把它代到这里
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  that will see a times t, you put this expression.
  这里就有at 带入表达式
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  So what will you get?
  你将会得到什么
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  We'll get an expression in which there is no t;
  我们现在得到了一个不含t的表达式
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  t has been banished in favor of v.
  t被v替换掉了