来自《耶鲁大学开放课程：基础物理 第11集 第11集》

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  I'm trying to pick a direction.
  我现在要选定方向
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  Either direction, in this case,
  在这个例子中 无论哪个方向
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  is going to be out of the blackboard or into the blackboard.
  不是向黑板外指 就是指向黑板里
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  And the convention is stated in many different ways.
  有多种方法可以确定它的方向
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  One convention is, you take this r,
  一种方法是 你取这个 r
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  and you turn a screwdriver from r to F.
  然后从 r 旋转到 F
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  Okay? You guys imagine in your mind;
  你们自己在脑海里想象一下
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  take a screwdriver,
  取一把螺丝刀
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  turn the screwdriver from r to F.
  从 r 转到 F
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  Which way will this--That's right. You see.
  哪一种方法会...对的 看来你懂了
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  That's what all the rap guys are doing.
  说唱歌手就是这么干的
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  They're trying to use the right-hand rule,
  他们试图使用右手法则