题目内容
如图所示,让一滑块以初速度
从A点出发,沿两个不同的轨道滑行分别到达C点或D点后水平抛出。已知两个轨道是固定的而且光滑,A、B、E在同一水平地面上, C、D、E在同一竖直线上,D点距地面的高度为h,C点高度为2h, 重力加速度为g。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241456078134579.jpg)
(1)求滑块沿ABC滑道和ABD滑道运动,最后最后平抛的落点与E点间的距离sC和sD;
(2)如果要求sC >sD,那么滑块的初速度
应满足什么条件?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607236323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241456078134579.jpg)
(1)求滑块沿ABC滑道和ABD滑道运动,最后最后平抛的落点与E点间的距离sC和sD;
(2)如果要求sC >sD,那么滑块的初速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607236323.png)
(1)sC
, sD
(2)
>![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608079542.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607923968.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607969921.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607236323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608079542.png)
试题分析:(1)(8分)根据机械能守恒得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608141892.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608203857.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608266630.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608406597.png)
联解以上各式的 sC
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607923968.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607969921.png)
(2)(4分)要sC >sD,即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608703947.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608765896.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145607236323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145608079542.png)
点评:本题关键是分析清楚两次滑块的运动情况,然后对滑块的各个运动过程运用相应的规律列式求解.
![](http://thumb2018.1010pic.com/images/loading.gif)
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