题目内容
如图(a),平行金属板A和B间的距离为d ,它们的右端安放着靶MN(可金属板右侧上下移动也可在纸面内转动),现在A、B板上加上如图(b)所示的方波形电压,t=0时A板比B板的电势高,电压的正向值为U0,反向值也为U0.现有由质量为m的带正电且电荷量为q的粒子组成的粒子束,从AB的中点O以平行于金属板方向OO/的速度大小为
持续不断射入,所有粒子在AB间的飞行时间均为T,且不会与金属板相碰,不计重力影响.求:
(1)金属板长度
(2)粒子飞出电场时位置离O/点的距离范围
(3)要使粒子能全部打在靶MN上,靶MN的长度至少多大?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227446137448.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744597582.gif)
(1)金属板长度
(2)粒子飞出电场时位置离O/点的距离范围
(3)要使粒子能全部打在靶MN上,靶MN的长度至少多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227446137448.jpg)
(1)金属板的长度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744628380.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744644604.gif)
(2)当粒子由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744691251.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227447062116.gif)
当粒子由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744722502.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227447691004.gif)
所以,在距离O/中点下方
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744784564.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744800555.gif)
粒子在电场中运动时,加速度向下的时间是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744831258.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744847232.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227448621100.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122744878776.gif)
即所有的粒子平行射出电场,如下图所示,要使靶长度最小,需要将靶垂直于粒子出射方向放置……………(1分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227450494182.jpg)
靶长最小值
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241227451271661.gif)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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