题目内容
(10分)如图所示,A、B两棒的长均为L="1" m,A的下端和B的上端相距s="20" m.若A、B同时运动,A做自由落体运动,B做竖直上抛运动,初速度
="40" m/s.求:(g取10 m/s。)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241223110351966.jpg)
(1)A、B两棒何时相遇.
(2)A、B两棒从相遇开始到分离所需的时间.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311004205.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241223110351966.jpg)
(1)A、B两棒何时相遇.
(2)A、B两棒从相遇开始到分离所需的时间.
(1)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311051303.gif)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311066445.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311051303.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311066445.gif)
(1)设经过时间t1两棒相遇,由
(3分)
得
(1分)
(2)设经过时间如两棒分离,由
(3分)
解得:
(分)
所以两棒从相遇开始到分离所需的时间
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311082732.gif)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311097501.gif)
(2)设经过时间如两棒分离,由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311097833.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311129608.gif)
所以两棒从相遇开始到分离所需的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122311144546.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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