来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  and the derivative of the velocity is called the acceleration,
  速度的导数被称为"加速度"
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  and we write it as the second derivative of position.
  我们把它写成位移的二阶导数
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  So I'm hoping you guys are
  我希望你们
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  comfortable with the notion of taking one or two
  能习惯求一阶 二阶
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  or any number of derivatives.
  或者任意阶导数的概念
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  Interestingly, only the first two derivatives have a name.
  有趣的是 只有前两阶导数有名字
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  The first one is velocity, the second one is acceleration.
  一阶导数叫速度 二阶导数叫加速度
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  The third derivative, unfortunately, was never given a name,
  遗憾的是三阶导数没有专门的名称
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  and I don't know why.
  我也不知道这是为什么
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  I think the main reason is that there are no equations
  我想主要原因是因为还没有等式
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  that involve the third derivative explicitly.
  明显涉及三阶导数
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  F=ma. The a is this fellow here,
  F=ma a就是这里的这个