题目内容
(16分)两个板长均为L的平板电极,平行正对放置,相距为d,极板之间的电势差为U,板间电场可以认为是均匀的。一个α粒子从正极板边缘以某一初速度垂直于电场方向射入两极板之间,到达负极板时恰好落在极板边缘。已知质子电荷为e,质子和中子的质量均视为m,忽略重力和空气阻力的影响,求:
(1)极板间的电场强度E;
(2)α粒子的初速度v0。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241210436063045.jpg)
(1)极板间的电场强度E;
(2)α粒子的初速度v0。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241210436063045.jpg)
(1)E=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043606344.gif)
(2)v0=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638372.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638438.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043606344.gif)
(2)v0=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638372.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638438.gif)
(1)板间场强E=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043606344.gif)
(2)α粒子(2e,4m)受电场力F=2eE =
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043684397.gif)
α粒子加速度a=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043700375.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043716435.gif)
∵类平抛
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043731111.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043747213.gif)
L=v0t
∴ v0=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638372.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121043638438.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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