题目内容
如图所示,在倾角为30°的光滑斜面上放置质量分别为m和2m的四个木块,其中两个质量为m的木块间用一不可伸长的轻绳相连,木块间的最大静摩擦力是Ffm.现用平行于斜面的拉力F拉其中一个质量为2m的木块,使四个木块沿斜面以同一加速度向下运动,则拉力F的最大值是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437562951851.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437562951851.jpg)
A.![]() | B.![]() |
C.2Ffm | D.Ffm |
C
设四个木块沿斜面向下运动的最大加速度为
,则对两个质量为m的木块和上面的一个质量为2m的木块有:
,解得
,此时上面的两个木块间的静摩擦力为合
,所以上面的两个木块不会出现相对滑动。对整体有:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437572311072.png)
,解得
,即C选项正确
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143756623379.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437568571123.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437570911001.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143757153587.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241437572311072.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143757465891.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143757528706.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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