题目内容
如图所示,光滑斜面的倾角都是a,球的质量都是m,球都用轻绳系住静止在斜面上,甲的悬线与斜面平行,乙的悬线沿水平方向,丙的悬线沿竖直方向,丁的悬线与水平面的夹角大于a。关于球对斜面压力的大小FN有下列说法:①甲图FN一定最大;②乙图FN一定最大;③丙图FN一定为零;④丁图FN可能最小。以上说法正确的有 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316436423479.png)
A.只有①④ | B.只有②③ | C.只有①③ | D.只有②④ |
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316436423479.png)
B
甲:
,乙:
,丙:
。丁:
所以B对。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131643673839.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316442191032.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131644266544.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316442971083.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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