题目内容
如图所示,小球被轻质的细绳系着,斜吊着放在光滑的斜面上.小球质量为m,斜面倾角为
.现向右缓慢推斜面,在推动过程中绳上张力的最小值是______________.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241454521531792.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452091297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241454521531792.png)
mgsin![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452091297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452091297.png)
试题分析:如下图对小球进行受力分析,当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452263364.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452309411.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452668605.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145452715898.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241454527934695.png)
点评:中等难度。此题属于合力大小、方向不变,一个力方向不变,求另一个力的最小值问题,解决方法是过合力箭首做方向不变的力的平行线,另一个力的箭首肯定落在这条平行线上,其中与平行线垂直的最小。
![](http://thumb2018.1010pic.com/images/loading.gif)
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