题目内容
如图所示,在空间中存在垂直纸面向里的磁感应强度为B匀强磁场,其边界AB、CD的宽度为d,在左边界的Q点处有一质量为m,带电量为负q的粒子沿与左边界成30o的方向射入磁场,粒子重力不计.求:
(1)带电粒子能从AB边界飞出的最大速度?
(2)若带电粒子能AB边界飞出磁场,粒子在磁场中运动的时间?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514052764947.jpg)
(1)带电粒子能从AB边界飞出的最大速度?
(2)若带电粒子能AB边界飞出磁场,粒子在磁场中运动的时间?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514052764947.jpg)
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151405463803.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514052921064.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151405463803.png)
试题分析:(1)粒子能从AB边界射出,临界情况有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151405619761.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151405682784.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514058851544.png)
所以粒子能从左边界射出速度应满足
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514052921064.png)
(2)粒子能从AB边界射出时,圆心角
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151406009527.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151406165781.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151406477724.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151405463803.png)
点评:此类题型解法一般为找圆心、定半径、画轨迹。
![](http://thumb2018.1010pic.com/images/loading.gif)
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