题目内容
(选修3-5).如图所示,一质量为M的平板车B放在光滑水平面上,在其右端放一质量为m的小木块A,m<M,A、B间粗糙,现给A和B以大小相等、方向相反的初速度
,使A开始向左运动,B开始向右运动,最后A不会滑离B,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006281263362.jpg)
(1)A、B最后的速度大小和方向;
(2)从地面上看,小木块向左运动到离出发点最远处时,平板车的速度大小和方向。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628095323.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006281263362.jpg)
(1)A、B最后的速度大小和方向;
(2)从地面上看,小木块向左运动到离出发点最远处时,平板车的速度大小和方向。
(1)
,方向向右 ;(2)
,方向向右
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628142711.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628157748.png)
试题分析:(1)最后A不会滑离B,即两者有共同速度,设为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628173268.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628189869.png)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628204779.png)
(2)A向左运动速度减为零时,到达最远处,设此时速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628220311.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628235747.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000628251810.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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