题目内容
如图所示,光滑斜面的倾角为30°,轻绳通过两个滑轮与A相连,轻绳的另一端固定于天花板上,不计轻绳与滑轮的摩擦。物块A的质量为m,不计滑轮的质量,挂上物块B后,当动滑轮两边轻绳的夹角为90°时,A、B恰能保持静止,则物块B的质量为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250032109382123.jpg)
A.
m B.
m
C.m D.2m
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250032109382123.jpg)
A.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003210953413.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003210969344.png)
C.m D.2m
A
试题分析:先对A受力分析,再对B受力分析,如图
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250032110007266.png)
设物体B的质量为M,根据共点力平衡条件,有mgsin30°=T
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003211016336.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003210953413.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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