题目内容
如图所示,木板OA水平放置,长为L,在A处放置一个质量为m的物体,现绕O点缓慢抬高到A处,直到当木板转到与水平面成α角时停止转动.这时物体因受到一个微小的干扰而开始缓慢匀速下滑,最后到达O点,则在整个过程中( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250012331826224.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250012331826224.png)
A.支持力对物体做的总功为mgLsina |
B.摩擦力对物体做的总功为零 |
C.木板对物体做的总功为零 |
D.木板对物体做的总功为正功 |
AC
试题分析:在木板转动的过程中,物体相对于木板没有滑动,静摩擦力与运动方向垂直,物体受到静摩擦力对物体做功为零,在物体匀速下滑时,受到的滑动的摩擦力对物体做功为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001233198867.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001233214658.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001233214925.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001233229635.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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