题目内容
如图所示,用一根细线系住重力为
、半径为
的球,其与倾角为
的光滑斜面劈接触,处于静止状态,球与斜面的接触面非常小,当细线悬点
固定不动,斜面劈缓慢水平向左移动直至绳子与斜面平行的过程中,下述正确的是( ).
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250011067902156.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106727316.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106743303.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106758310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106774292.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250011067902156.jpg)
A.细绳对球的拉力先减小后增大 |
B.细绳对球的拉力先增大后减小 |
C.细绳对球的拉力一直减小 |
D.细绳对球的拉力最小值等于![]() |
C
试题分析:以小球为研究对象,其受力分析如图所示:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250011068211749.jpg)
因题中“缓慢”移动,故小球处于动态平衡,由图知在题设的过程中,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106836302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106836302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106868357.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106836302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001106899725.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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