来自《耶鲁大学开放课程：基础物理 第4集 第4集》

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  is to be able to predict something about the future,
  就是在给定当前的状态的情况下
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  given something about the present.
  去预测未来的一些事情
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  So, all problems that we solve can be categorized that way.
  我们解决的所有问题都能这样分类
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  So I'm going to take a very simple problem,
  我要讲一个很简单的问题
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  a problem to which I will return in great detail later on;
  待会我还会回来更具体地讲它
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  but let me first start with-- let me start with this problem,
  但是现在还是让我从这个问题开始
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  which I will do very quickly now
  我会讲得很快
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  and we'll come back and do it more slowly later.
  但待会我们再回来讲的时候 会慢很多
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  But at least it's a concrete problem.
  至少这是一个具体的问题
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  The problem looks like this.
  这个问题是这样的
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  So, here is a table and here's a spring and here's the mass m.
  有一张桌子 一根弹簧和一个物体 m
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  There's a force constant k.
  弹簧的弹性系数为 k