来自《耶鲁大学开放课程：基础物理 第3集 第3集》

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  and see what force it applies and divide by the acceleration
  看看它能提供多大的力 然后除以加速度
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  and get the mass, "
  得到质量"
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  because we haven't defined force, either.
  因为我们还没给力下一个定义
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  You've got to realize that.
  你必须意识到这点
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  Let me ask you something.
  我来问问你们吧
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  How do we decide how long a meter is?
  我们是如何决定一米有多长的
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  Can you tell me, how do you know how long a meter is?
  你能告诉我 你怎么知道一米有多长吗
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  Right.
  没错
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  And we'll call it.
  然后我们给它命名
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  First thing you've got to do is,
  首先你要做的是
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  realize that some of these things are not God-given.
  意识到这些并不是上帝赐予的
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  A meter, for example, is not deduced from anything.
  一米 打个比方 并不是推导得来的