题目内容
如图在光滑水平面上叠放AB两物体,其间有摩擦,mA=2 kg,mB=1 kg,速度的大小均为v0=10 m/s,设A板足够长,当观察到B做加速运动时,A的可能速度为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242015409021362.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242015409021362.png)
A.2 m/s | B.3 m/s | C.4 m/s | D.5 m/s |
C
试题分析:在摩擦力的作用下,因为B物体质量下,所以B物体先做减速运动,后来有反向做加速运动,A一直做减速运动,最终当两物体速度相等时,一起匀速设最终速度为v,根据系统动量守恒有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201541979866.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201543024719.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201544085648.png)
设B的速度为零时,A的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201544849308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201545972789.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201546908584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201548000491.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201548578495.png)
故选C
点评:本题运用动量守恒定律分析物体的运动状态,也可以运用牛顿第二定律和运动学公式分析.
![](http://thumb2018.1010pic.com/images/loading.gif)
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