题目内容
如图所示,一带电粒子从平行带电金属板左侧中点垂直于电场线以速度v0射入电场中,恰好能从下板边缘以速度v1飞出电场.若其它条件不变,在两板间加入垂直于纸面向里的匀强磁场,该带电粒子恰能从上板边缘以速度v2射出.不计重力,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020155672039.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020155672039.jpg)
A.2v0= v1+v2 | B.v0=![]() | C.v0=![]() | D.v0<v1=v2 |
B
试题分析:带点粒子在电场中运动时,电场力做正功,在电场和磁场的复合场中运动时,洛伦兹力不做功,电场力做负功,所以有v2<v0<v1,对以上两个过程运用动能定理:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020156141028.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020156301027.png)
联立解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002015645759.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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