题目内容
(10分)如图所示,一段长为L =" 1" m的棒,上端悬挂在天花板上P点,棒的正下方固定着一个高为d =" 1" m的中空圆筒Q。棒被释放后自由落下,它通过圆筒所需时间为t =" 0.5" s。求:圆筒上缘离天花板的距离h。(g 取10 m / s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019058822411.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019058822411.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001905929731.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019059443920.png)
试题分析:圆筒下落为自由落体运动,设从开始下落到棒的下端运动到圆筒的上缘(如图1)用时为t1,下落到棒离开(如图2)用时为t2,由自由落体运动特点得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001905960737.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001905976861.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001906069791.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001906085928.png)
棒通过圆筒的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001906100440.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001905929731.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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