题目内容
如图,水平匀强电场的电场强度为E,一个带电小球质量为m,轻质的绝缘细线长为L,静止时小球位于A点,细线与竖直方向成30°角, 求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006369871643.png)
(1)小球带何种电荷?电荷量多少?(5分)
(2)现将小球拉回到竖直方向(图中B点),后由静止释放,小球通过A点位置时的速度大小是多少?(5分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006369871643.png)
(1)小球带何种电荷?电荷量多少?(5分)
(2)现将小球拉回到竖直方向(图中B点),后由静止释放,小球通过A点位置时的速度大小是多少?(5分)
(1)负,
(2)
(用三角函数表示也可以)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000637003706.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000637018951.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006370343694.jpg)
试题分析:(1)受力分析如图所示,所以小球带负电,由物体平衡
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000637049802.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000637065892.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000637003706.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006370961389.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006371121009.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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