题目内容
分)一带电质点从图中的A点竖直向上射入一水平方向的匀强电场中,质点运动到B点时,速度方向变为水平,已知质点质量为m,带电量为q,AB间距离为L,且AB连线与水平方向成
角,求(注意:图中vA、vB未知)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015239871548.png)
(1)质点从A运动到B时间;
(2)电场强度E;
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001523972294.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015239871548.png)
(1)质点从A运动到B时间;
(2)电场强度E;
(1)
; (2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524003823.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524018850.png)
试题分析: 质点受两个力作用:竖直方向的重力和水平方向的电场力;
(1)在竖直方向,做竖直上抛运动,上升过程可能反过来看成自由落体运动求解。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524034791.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524003823.png)
(2)在水平方向,做初速度为0的匀加速运动,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524065694.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524081838.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001524018850.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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