题目内容
如图所示是给墙壁粉刷涂料用的“涂料滚”的示意图。使用时,用撑竿推着粘有涂料的涂料滚沿墙上下缓缓滚动,把涂料粉刷到墙上.撑竿的重力和墙壁的摩擦均不计,且撑竿足够长,粉刷工人站在离墙壁一定距离处缓缓上推涂料滚,设该过程中撑竿对涂料滚的推力为F1,涂料滚对墙壁的压力为F2,则( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241438102262574.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241438102262574.png)
A.F1增大,F2减小 |
B.F1增大,F2增大 |
C.F1减小,F2减小 |
D.F1减小,F2增大 |
C
以涂料滚为研究对象,分析其受力,把杆对涂料滚的推力正交分解,有
,当涂料滚上移时,θ减小,F1减小,F2减小.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241438103822753.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143810288891.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241438103822753.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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