题目内容
用细线悬挂一质量为M的木块,木块静止,如图8-5-4所示.现有一质量为m的子弹自左方水平地射穿此木块,穿透前后子弹的速度分别为v0和v.求木块能摆到的最大高度.(设子弹穿过木块的时间很短,可不计)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818526919.jpg)
图8-5-4
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818526919.jpg)
图8-5-4
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818542629.gif)
由子弹和木块组成的系统在水平方向上不受外力,满足动量守恒.即mv0=mv+Mv′,v′=
(v0-v).木块以速度v′摆起过程中,只有重力做功,机械能守恒.即
Mv′2=Mghm,hm=
,所以hm=
.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818557387.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818573225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818589378.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120818542629.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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