题目内容
图中的车厢质量为M,长度为L,静止在光滑水平面上,质量为m的小木块以v0的速度无摩擦地在车厢底板上向右运动,木块与前车壁碰撞后以
的速度向左运动,则经过多长时间,木块将与后车壁相碰( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141245162389.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124391241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141245162389.jpg)
A.L/v0 | B.2ML/(3m+M)v0 |
C.mL/(M+m)v0 | D.ML/(M+m)v0 |
B
设向右为正方向,根据动量守恒定律有
mv0=Mv′-m
,解得碰后车厢的速度v′=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124641493.gif)
方向向右,经过时间t与后车壁相碰
L=
t+v′t,得t=
.
mv0=Mv′-m
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124391241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124641493.gif)
方向向右,经过时间t与后车壁相碰
L=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124391241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114124703662.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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