题目内容
如图所示,有一质子(质量为m,电荷量为e)由静止开始经电压为U1的电场加速后,进入两块板间距离为d,板间电压为U2的平行金属板间,若质子从两板正中间垂直电场方向射入偏转电场,并且恰能从下板右边缘穿出电场。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026067403267.jpg)
求:(1)质子刚进入偏转电场U2时的速度;
(2)质子在偏转电场U2中运动的时间和金属板的长度;
(3)质子穿出偏转电场时的动能。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026067403267.jpg)
求:(1)质子刚进入偏转电场U2时的速度;
(2)质子在偏转电场U2中运动的时间和金属板的长度;
(3)质子穿出偏转电场时的动能。
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606802880.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606755826.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606771866.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606786847.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606802880.png)
试题分析:(1) 质子在加速电场中有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606818168.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606849814.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606755826.png)
(2)质子在偏转电场中的运动可分解为水平方向的匀速直线运动和竖直方向的匀加速直线运动
水平方向
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606880465.png)
竖直方向
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606896722.png)
加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606927765.png)
由以上各式解得极板长
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606786847.png)
运动时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606771866.png)
(3)质子在整个运动过程中由动能定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606989822.png)
质子射出电场时的动能
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002606802880.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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