来自《耶鲁大学开放课程：基础物理 第2集 第2集》

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  if the speedometer says 60 miles per hour,
  如果速率表显示的是60英里每小时
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  you might say it's not accelerating.
  你也许会说它没有在加速
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  That's the layperson's view.
  但那是外行人的看法
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  If it's going in a circle,
  如果它在一个圆周上运动
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  you will say from now on, that it, indeed, has an acceleration,
  你会说从现在起它其实有加速度
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  even though no one's stepping on the accelerator,
  即使没有人去踩油门
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  of amount v^2 over R.
  加速度大小为 v^2 / R
• 
  
  That's a very important thing.
  这一点非常重要
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  That's what you're learning in this course.
  这就是你们在这门课上需要学习的
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  The fact that when you step on your gas you accelerate, everybody knows.
  所有人都知道踩油门就能加速
• 
  
  The fact that when you go in a circle, you accelerate
  而当你做圆周运动时你也在加速
• 
  
  is what we're learning here,
  这是我们在这里所学到的