题目内容
质量为m的物体从地面上方H高处无初速释放,陷入地面的深度为h,如图所示,在此过程中( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546385562192.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546385562192.png)
A.重力对物体做功为mgH |
B.重力对物体做功为mg(H+h) |
C.外力对物体做的总功为零 |
D.地面对物体的平均阻力为mg(H+h)/h |
BCD
试题分析:根据重力做功的公式可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154638634860.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154638743659.png)
对整个过程运用动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154639258895.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154639414907.png)
点评:该题是动能定理和重力做功公式的直接应用,要注意重力做功只跟高度差有关,难度不大.
![](http://thumb2018.1010pic.com/images/loading.gif)
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