来自《耶鲁大学开放课程：基础物理 第9集 第9集》

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  "What is the total (1/2)·m·v^2
  "所有粒子的 (1/2)·m·v^2
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  summed over all the particles?"
  总和是多少"
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  For that purpose,
  为此
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  it's convenient to take the following simpler rigid body.
  选一个这种比较简单的刚体会很方便
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  We take a rigid body by taking a mass m1 at a distance R1,
  我们选取的刚体质量为 m1 到转轴距离为 R1
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  connected to some central hub with a massless rod,
  用一根无质量的细杆与转轴相连
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  and you take another mass,
  再拿第二个物体
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  and you take a third mass.
  和第三个物体
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  This is m2, at a distance R2,
  这个质量 m2 距离为 R2
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  there's m3, at a distance R3, and so on.
  这个质量 m3 距离为 R3 等等
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  You can make a rigid body
  你可以用这种简单的方法
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  by modeling it in this simple fashion.
  构造一个刚体