题目内容
如图,一质量为M的物块静止在桌面边缘, 桌面离水平面的高度为h.一质量为m的子弹以水平速度v0射入物块后, 以水平速度v0/2射出. 重力加速度为g. 求
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707375599583.png)
(1)此过程中系统损失的机械能;
(2)此后物块落地点离桌面边缘的水平距离。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707375599583.png)
(1)此过程中系统损失的机械能;
(2)此后物块落地点离桌面边缘的水平距离。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707380891321.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707385101051.png)
试题分析:(1)设子弹穿过物块后物块的速度为V,由动量守恒得
mv0=m
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170739150209.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170739524290.png)
系统的机械能损失为
ΔE=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170739945529.png)
由②③式得
ΔE=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170740164382.png)
(2)设物块下落到地面所需时间为t,落地点距桌面边缘的水平距离为s,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170740382278.png)
s=Vt ⑥
由②⑤⑥得
S=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170740803349.png)
点评:本题采用程序法按时间顺序进行分析处理,是动量守恒定律与平抛运动简单的综合,比较容易.
![](http://thumb2018.1010pic.com/images/loading.gif)
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