题目内容
一根竖直杆悬挂着,杆被分为等长的2节,开始时杆的下端恰在窗口的上边沿。剪断悬绳后,它的下一节通过窗口上边沿的时间为t,那么它的上一节通过窗口的上边沿所经历的时间为 。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556108562.png)
设杆全部通过窗口的上边沿的时间为t
,每节杆的长度为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556248280.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556280739.png)
第一节通过窗口的上边沿:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241255562951011.png)
解得,
=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556451360.png)
所以上一节通过窗口的上边沿所经历的时间为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556467438.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556108562.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556217286.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556248280.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556280739.png)
第一节通过窗口的上边沿:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241255562951011.png)
解得,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556404370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556451360.png)
所以上一节通过窗口的上边沿所经历的时间为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556467438.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125556108562.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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