题目内容
三段不可伸长的细绳OA、OB、OC能承受的最大拉力相同均为200N,它们共同悬挂一重物,如图所示,其中OB是水平的,A端、B端固定,θ=300。则O点悬挂的重物G不能超过( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601501431402.png)
A.100N B.173N C.346N D.200N
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601501431402.png)
A.100N B.173N C.346N D.200N
A
试题分析:以结点O为研究,在绳子均不被拉断时受力分析可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160150237928.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601504081017.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160150502607.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241601506891166.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160150923654.png)
故选A,
点评:本题首先要选择研究对象:结点O;其次关键是作好力图,就能直观比较三个绳子拉力的大小.
![](http://thumb2018.1010pic.com/images/loading.gif)
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