题目内容
(9分)如图所示,将一根长为2d的不可伸长的细绳两端固定在相距为d的AB两等高点,绳上挂一小滑轮P,P下面有一质量为m的物体处于静止状态。现用水平力F拉住滑轮使AP处于竖直方向。若不计绳与滑轮摩擦及空气阻力,也不计绳与滑轮的质量。求水平力F的大小。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241218183003639.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241218183003639.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818316427.gif)
设AP间离为h则由几何关系得
(2分)
得
(1分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241218184724203.jpg)
对滑轮受力分析,有
(2分)
(2分)
解得:
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818332501.gif)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818456397.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241218184724203.jpg)
对滑轮受力分析,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818488503.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818503426.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121818316427.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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