来自《耶鲁大学开放课程：基础物理 第10集 第10集》

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  Okay?
  懂了吗
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  All right, so that's one demonstration of the Parallel Axis Theorem,
  这就是平行轴定理的典型范例之一
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  of the proof of the Parallel Axis Theorem.
  也是平行轴定理的证明
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  Now I'm going to show you a similar result,
  现在我要向你告诉一个类似的结论
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  because that's going to be also useful in the study of rigid bodies.
  因为它对于我们研究刚体也是很用的
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  It has the very same flavor, so I want to do that side-by-side.
  它们形式类似 所以我要对比来做
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  And that's the following question.
  问题是这样的
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  Suppose you have, in two dimensions,
  假设在二维空间里
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  a whole bunch of masses:
  有很多个物体
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  m1 with the location r1,
  m1 在 r1 处
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  m2 with a location r2, and they're all moving around.
  m2 在 r2 处 它们都在运动
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  You know that given all the masses that it's something, some right here,
  给定所以物体的质量及其位置