题目内容
用轻弹簧竖直悬挂质量为的物体,静止时弹簧伸长量为L .现用该弹簧沿斜面方向拉住质量为2
的物体,系统静止时弹簧伸长量也为L . 斜面倾角为30°,如图所示.则物体所受摩擦力( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500235683812021.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356822337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500235683812021.jpg)
A.等干零 |
B.大小为![]() |
C.大小为![]() |
D.大小为![]() |
A
试题分析:弹簧竖直悬挂物体时,对物体受力分析,根据共点力平衡条件
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356900511.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356916461.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500235693214750.jpg)
根据共点力平衡条件,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356947986.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356963494.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002356978384.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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