题目内容
如图所示,将一球形物体夹在竖直墙AC与木板BC之间,已知各接触面均光滑,将球对墙的压力用N1表示,球对木板的压力用N2表示.现将木板以C端为轴缓慢地转至水平位置的过程中,下列说法中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241512413792561.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241512413792561.png)
A.N1和N2都增大 | B.N1和N2都减小 |
C.N1增大, N2减小 | D.N1减小, N2增大 |
B
试题分析:如图对小球进行受力分析,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241504468.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241629492.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241504468.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241629492.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241925383.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241504468.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151242034424.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151241629492.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241512422534021.png)
故选B
点评:中等难度。 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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