来自《耶鲁大学开放课程：基础物理 第5集 第5集》

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  namely a certain force.
  就是一个恒定的外力
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  So, I'm going to write here
  我要写在这里
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  as you can imagine F / m in the place of a,
  你可以想到 F / m 就是 a
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  but I'm going to make one more cosmetic change in notation.
  但我现在要对这个符号进行一下改动
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  In all these energy formulas,
  在所有能量方程中
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  rather than calling the initial velocity or initial anything
  初速度或任何初始量的下标为 0
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  with subscript zero and the final is no subscript,
  而末态量没有下标
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  we are going to use a notation where
  我们要用符号标注一下
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  the final quantities are denoted with a subscript 2,
  令末态量的下标为 2
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  initial quantities are denoted by a subscript 1.
  初始量的下标为 1
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  In other words, initially, the body had a velocity of v1,
  换种说法 开始物体的速度为 v1
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  and then it had an acceleration a for a distance d,
  然后在 d 距离里 有一个加速度 a