题目内容
如图所示,水平细杆上套一细环A,环A与球B间用一轻质绳相连,质量分别为mA和mB且mA=2mB,由于B球受到水平风力作用,A环与B球一起向右匀速运动.已知细绳与竖直方向的夹角为
.则下列说法错误的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241505547644577.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150554671292.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241505547644577.jpg)
A.B球受到的风力F为mA gtan![]() |
B.A环与水平细杆间的动摩擦因数为![]() ![]() |
C.若水平风力增大,杆对A环的支持力保持不变 |
D.若水平风力增大,轻质绳对B球的拉力保持不变 |
AD
试题分析:B球受到重力,绳子的拉力,风力作用处于平衡状态,所以根据矢量三角形可得B受到的风力为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150554983748.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555076650.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555154998.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555232442.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555295742.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241505554201007.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555498667.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555295742.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150555076650.png)
点评:做此类型的题目,一定要注意变力和恒力,在矢量三角形中用三角函数解题
![](http://thumb2018.1010pic.com/images/loading.gif)
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