题目内容
如下图是用来粉刷墙壁的涂料滚的示意图。使用时,用撑竿推着涂料滚沿墙壁上下滚动,把涂料均匀地粉刷到墙壁上。撑竿的重量和墙壁的摩擦均不计,而且撑竿足够长。粉刷工人站在离墙壁某一距离处缓缓上推涂料滚,使撑杆与墙壁间的夹角越来越小。该过程中撑竿对涂料滚的推力为
,涂料滚对墙壁的压力为
,下列说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019365522598.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936505333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936520353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019365522598.jpg)
A.![]() ![]() | B.![]() ![]() |
C.![]() ![]() | D.![]() ![]() |
D
试题分析:以涂料滚为研究对象,分析受力情况,作出力图.设撑轩与墙壁间的夹角为α,根据平衡条件得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936692710.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936692724.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936708413.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936723498.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001936739448.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500193675415156.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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