题目内容
如图所示,已知正方形abcd边长为
,e是cd边的中点,abcd所围区域内是一个磁感应强度大小为B、方向垂直于纸面的匀强磁场,一带电粒子从静止开始经电压为U的电场加速后从a点沿ab方向射入磁场,最后恰好从e点射出。不计带电粒子的重力。求:
(1)带电粒子的电量与质量的比值q/m;
(2)带电粒子从a点到e点的运动时间。
(已知sin53o=0.8 cos53o=0.6 tan26.5o=
)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159392172752.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939030185.gif)
(1)带电粒子的电量与质量的比值q/m;
(2)带电粒子从a点到e点的运动时间。
(已知sin53o=0.8 cos53o=0.6 tan26.5o=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939045225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159392172752.gif)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939264640.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939295544.gif)
(1) 粒子经电场加速后,由动能定理得:
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159393423962.jpg)
射入磁场后,有:
(2分)
粒子在磁场中的运动轨迹如图所示,几何关系是:
(2分)
解得带电粒子的电量与质量的比值为:
(2)由几何关系得 tanα=
α=26.5oβ=127o(2分)
(1分) T=
(1分)
T=
(1分)
t=
(2分)
解得 t=
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939326522.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159393423962.jpg)
射入磁场后,有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939373520.gif)
粒子在磁场中的运动轨迹如图所示,几何关系是:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939388602.gif)
解得带电粒子的电量与质量的比值为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939264640.gif)
(2)由几何关系得 tanα=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939045225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939482531.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939498380.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939513128.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939529467.gif)
t=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939544508.gif)
解得 t=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115939607643.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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