题目内容
如图,重量为G的物体A在大小为F的水平向左恒力作用下,静止在倾角为α的光滑斜面上.下列关于物体对斜面压力N大小的表达式,正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241516183601372.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241516183601372.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
ABD
试题分析:如图对A进行受力分析
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241516191716766.png)
A、由三角函数关系得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619234737.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619358746.png)
B、由勾股定理可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619483735.png)
C、根据正交分解法可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619624872.png)
D、以F为已知量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619733730.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151619842731.png)
故选ABD
点评:中等难度。共点力平衡问题可以用力的合成法求解,也可以用力的分解法求解,还可以用正交分解法求解.
![](http://thumb2018.1010pic.com/images/loading.gif)
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