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 spring is getting squashed on either side,
  这个弹簧两边都会受到压缩
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  and it'll squash by certain amount x,
  压缩量为 x
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  that depends on your mass,
  它由你的质量决定
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  and that x will be turned into a motion of a needle
  x 会转换成指针的运动
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  and that'll read your mass.
  你从而可以读数
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  Now, what happens if the elevator is accelerating upwards
  现在如果电梯向上以加速度 a 运动
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  with an acceleration a?
  会发生什么呢
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  That's the question.
  这就是问题
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  The way I analyze it is,
  我们这样来分析
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  I say, if I look at me and I write the forces on me,
  如果只考虑我 我分析出我所受的力
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  that is mg acting down,
  先是向下的 mg
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  then we use w as the symbol to
  然后我们用 w 来表示