题目内容
如图所示,A、B两小球带等量同号电荷,A固定在竖直放置的L=10cm长的绝缘支杆上,B受A的斥力作用静止于光滑的绝缘斜面上与A等高处,斜面倾角为
=300,B的质量为m=360g。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019573932709.jpg)
求:(1)B球对斜面的压力大小
(2)B 球带的电荷量大小(g取10m/s2,结果保留两位有效数字)。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957362299.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019573932709.jpg)
求:(1)B球对斜面的压力大小
(2)B 球带的电荷量大小(g取10m/s2,结果保留两位有效数字)。
(1)0.2N;(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957409844.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957409844.png)
试题分析:令 B球对斜面的支持力为FN,带的电荷量Q,A、B相距r。
对B球受力分析如图示
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019574403407.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957456778.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957471681.png)
据牛顿第三定律 B球对斜面的压力
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957487689.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019575021072.png)
又
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957502561.png)
代入数据得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001957409844.png)
(用其他方法只要合理正确同样给分)
![](http://thumb2018.1010pic.com/images/loading.gif)
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