来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  The unit for time will be a second,
  时间的单位是"秒"
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  and time will be measured in seconds.
  时间都是按秒来计的
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  Then we'll come to other units.
  以后还会遇上其它单位
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  Right now, in kinematics,
  目前 在运动学中
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  this is all you need.
  这些就足够了
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  Now, there are some tricky problems in the book.
  咱们书上有些题目会有陷阱
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  Sometimes they give you the speed in miles per hour,
  有时候速度的单位是英里/小时
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  kilometers per year,
  千米/年
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  pounds per square foot.
  英磅/平方米
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  Whatever it is,
  不管是什么
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  you've got to learn to transform them,
  你得学会换算
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  but I won't do them.
  但我就不去做了