题目内容
(10分)如图所示,两带电平行板竖直放置,开始时两板间电压为U,相距为d,两板间形成匀强电场。有一带电粒子质量为m(重力不计)、所带电量为+q,从两板下端连线的中点P以竖直速度v0射入匀强电场中,使得带电粒子落在A板M点上,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009536886662.png)
试求:(1)M点离板下端的高度;
(2)若将A板向左侧水平移动d/2并保持两板电压为U,此带电粒子仍从P点竖直射入匀强电场且仍落在A板M点上,则应以多大的速度v射入匀强电场?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009536886662.png)
试求:(1)M点离板下端的高度;
(2)若将A板向左侧水平移动d/2并保持两板电压为U,此带电粒子仍从P点竖直射入匀强电场且仍落在A板M点上,则应以多大的速度v射入匀强电场?
见解析
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000953703918.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009537191093.png)
解得M点离板下端的高度
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000953735968.png)
(2)电压不变,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000953766759.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000953781555.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000953797159.png)
由式
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009538281047.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009538441217.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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