题目内容
把质量0.2g的带负电的小球A用绝缘线挂起,现将带电为Q=4.0×
C的带电小球B靠近A,两球在同一水平面上,相距30cm,此时A球悬线与竖直方向成45°而平衡,如图所示,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845319440.gif)
①B球受到的库仑力大小;
②A球电量;
③B在球A平衡处的场强.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845319128.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845319440.gif)
①B球受到的库仑力大小;
②A球电量;
③B在球A平衡处的场强.
(1)2×
N (2)5×10-7C (3)4×103N/C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845334123.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845350519.gif)
(1)T=mg/cos
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411584536696.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411584536696.gif)
∴f=mg=2×
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845334123.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115845412702.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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