题目内容
如图所示,重20 N的物体放在粗糙水平面上,用F="8" N的力斜向下推物体。F与水平面成30°角,物体与平面间的动摩擦因数μ=0.5,则物体
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250033555052606.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250033555052606.jpg)
A.对地面的压力为28 N | B.所受的摩擦力为4![]() |
C.所受的合力为5 N | D.所受的合力为0 |
BD
将力F根据作用效果分解如图所示,对地的压力为N=F2+G="Fsin" 30°+G="24" N,又因F1="Fcos" 30°<μN,故受到的静摩擦力为f="Fcos" 30°=4
N,故物体合力为零,所以B、D项正确。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250033557233527.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003355520344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250033557233527.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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