来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  So, that is a tricky problem to begin with
  所以这个问题刚开始的时候有点难度
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  because if you take this formula here,
  因为如果你要用这个公式
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  it tells you y if you know t,
  求y的时候就一定要知道t
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  but no, we're not saying that.
  但是 我们不知道
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  We don't know the time
  我们既不知道时间
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  and we don't know how high it's rising
  又不知道最高点的高度
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  so you can ask, "How am I supposed to deal with this problem?"
  那你就会问了 这道题该怎么做呢
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  Then you put something else that you know in your mind,
  然后你就想到了些东西
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  which is that the highest point
  也就是说 最高点
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  is the point when it's neither going up nor coming down.
  就是那个既不上升也不下降的点
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  If it's going up, that's not the highest point.
  如果它还在上升 那就不叫最高点
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  If it's coming down, that's not the highest point.
  如果它还在下降 那也不叫最高点