题目内容
如图所示,两个分别用长l = 5cm的绝缘细线悬挂于同一点的相同金属小球(可视为点电荷),带有等量同种电荷。由于静电力为斥力,它们之间的距离为
。已测得每个金属小球的质量
。试求它们所带的电荷量q。(已知
,
)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908488722049.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190847748497.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190847998759.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190848154591.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190848497888.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908488722049.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908489031247.png)
试题分析:带电金属小球在重力、静电力和线的拉力作用下,处于平衡状态,它的受力示意图如图所示。由图可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908491681914.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190849262666.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190849542784.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908498541011.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241908489031247.png)
点评:对小球进行受力分析,运用力的合成或分解结合共点力平衡条件解决问题.需要注意的是:两小球受到的库伦力是作用力与反作用力,大小相等,方向相反,作用在同一条直线上,作用在两个物体上.
![](http://thumb2018.1010pic.com/images/loading.gif)
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