题目内容
如图所示,一质量
的平顶小车静止在光滑的水平轨道上。车顶右端放一质量
的小物体,小物体可视为质点。现有一质量
的子弹以水平速度
射中小车左端,并留在车中,已知子弹与车相互作用时间极短,小物体与车间的动摩擦因数为
,最终小物体以
的速度离开小车,g取
。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250053278942186.png)
① 子弹刚刚射入小车时,小车的速度大小
;
② 小车的长度L。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327535702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327550662.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327566680.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327582607.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327613459.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327628560.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327660513.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250053278942186.png)
① 子弹刚刚射入小车时,小车的速度大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327909302.png)
② 小车的长度L。
①
②![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327940517.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327925611.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327940517.png)
试题分析:①子弹进入小车的过程中,子弹与小车组成的系统动量守恒,由动量守恒定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327956725.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327925611.png)
② 三物体组成的系统动量守恒,由动量守恒定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005328003858.png)
令小车长L,由功能关系知
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250053280181785.png)
联立并代入数值得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005327940517.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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