题目内容
如图10所示,质量相同的两个带电粒子P、Q以相同的速度沿垂直于电场方向射入两平行板间的匀强电场中,P从两极板正中央射入,Q从下极板边缘处射入,它们最后打在同一点(重力不计),则从开始射入到打到上板的过程中 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241435558942377.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241435558942377.png)
A.它们运动的时间tQ>tP |
B.它们运动的加速度aQ<aP |
C.它们所带的电荷量之比qP∶qQ=1∶2 |
D.它们的动能增加量之比ΔEkP∶ΔEkQ=1∶2 |
C
设P、Q两粒子的初速度是
,加速度分别是
和
,粒子P到上极板的距离是0.5h,它们类平抛的水平距离为l。则对P,由
,得到
,同理对Q,
,得到
。同时可见
,而
,可见
。由动能定理,它们的动能增加量之比
。综上,选C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143555988325.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556144347.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556206376.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556269975.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556347733.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556409999.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556612828.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556737717.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556830972.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143556955626.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241435570491315.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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