题目内容
如图,一质量为m的足球,以速度v由地面踢起,当它到达离地面高度为h的B点时 (取重力势能在A处为零势能面),下列说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824205403420568.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824205403420568.png)
A.在B点处的重力势能为mgh |
B.在B点处的动能为![]() |
C.在B点处的机械能为![]() |
D.在B点处的机械能为![]() |
AC
试题分析:从A到B过程中只有重力做功,机械能守恒,A点重力势能为0,动能为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824205407288586.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824205407288586.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824205407288586.png)
故选AC
点评:机械能等于重力势能与动能之和,
![](http://thumb2018.1010pic.com/images/loading.gif)
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