题目内容
如图所示柱体A的横截面是圆心角为
/2的扇形面,其弧形表面光滑,而与地面接触的下表面粗糙。在光滑竖直墙壁与柱体之间放置一质量为m的球体,系统处于平衡状态。若使柱体向右移动少许,系统仍处于平衡状态,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527513762745.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152751313309.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527513762745.jpg)
A.球对墙的压力增大 | B.柱体与球之间的作用力减小 |
C.柱体所受的摩擦力减小 | D.柱体对地面的压力增大 |
BC
试题分析:AB、对球体进行受力分析如图,随着柱体向右移动墙对球的支持力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152751391353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152751391353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527515636364.jpg)
CD、对柱体进行受力分析如下图,随着柱体向右移,柱体所受的摩擦力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152751578375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241527516565473.jpg)
故选BC
点评:作图法分析共点力平衡,首先找到不变的力,然后画出多组合力和分力的关系图就可以得到变化规律,这种方法直观、简单。
![](http://thumb2018.1010pic.com/images/loading.gif)
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