来自《耶鲁大学开放课程：基础物理 第3集 第3集》

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  This is the law that we all memorize and learn.
  这是一个我们都得学习牢记的定律
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  It says that, "If a body has an acceleration,
  它是这么说的 "如果一个物体有加速度
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  then you need a force
  那么你需要有一个力
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  and the relation of the force to acceleration is this thing."
  力和加速度的关系是这样的"
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  Now, I have to say a few words about units.
  我现在要讲一下单位的问题
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  Acceleration is measured in meters per second squared.
  加速度的单位是米每秒平方
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  Mass is measured in kilograms.
  质量的单位是千克
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  So, the way to measure force is in kilogram meters per second squared.
  所以 力的单位是千克米每秒平方
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  But we get tired of saying that long expression,
  但我们不想说得这么复杂
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  so we're going to call that a Newton, right?
  所以把这个单位称为"牛顿" 对吧
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  If you invented it,
  如果是你发明的
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  we'd call it whatever your name is,
  我们就用你的名字当单位