题目内容
如图所示,质量均为m的小车与木箱紧挨着静止在光滑的水平冰面上,质量为2m的 小明同学站在小车上用力向右迅速推出木箱后,木箱相对于冰面运动的速度大小为
,木箱与右侧竖直墙壁发生弹性碰撞,反弹后被小明接住,求整个过程中小明对木箱做的功.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040228692585.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004022838276.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040228692585.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004023041352.png)
试题分析:以向左为正方向,由动量守恒定律可得:
推出木箱过程中:(m+2m)v1-mv=0,
接住木箱过程中:mv+(m+2m)v1=(m+m+2m)v2,
设小明对木箱做功为W,对木箱由动能定理得:
W=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004023056338.png)
解得:W=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004023041352.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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