题目内容
(10分)在水平向右的匀强电场中,有一质量为m、带正电的小球,用长为L的绝缘细线悬挂于O点,当小球处于A点时静止,细线与竖直方向夹角为a(如图所示),现在A点给小球一个垂直于悬线的初速度v0,使小球恰能在竖直平面内做圆周运动,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250004546663432.jpg)
(1)在A点给小球的初速度v0多大?
(2)此过程中小球所受的最大拉力与最小拉力之差为多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250004546663432.jpg)
(1)在A点给小球的初速度v0多大?
(2)此过程中小球所受的最大拉力与最小拉力之差为多大?
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454698700.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454682715.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454698700.png)
试题分析:如图所示,重力与电场力的合力:F=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454713602.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454744839.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454760702.png)
由动能定理-mg×2Lcosα-mgtanα×2Lsinα=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454791756.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454807797.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454713602.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454838565.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454854593.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000454698700.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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