题目内容
如图3所示,地面上某区域存在着竖直向下的匀强电场,一个质量为m 的带负电的小球以水平方向的初速度v0由O点射入该区域,刚好通过竖直平面中的P点,已知连线OP与初速度方向的夹角为45°,则此带电小球通过P点时的动能为 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241414494844175.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241414494844175.png)
A.mv02 | B.![]() | C.2mv02 | D.![]() |
D
由题意可知小球到P点时水平位移和竖直位移相等,即v0t=
vPyt
合速度vP=
=
v0
EkP=
mvP2=
mv02,故选D.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141449577338.png)
合速度vP=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141450030646.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141450233322.png)
EkP=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141449577338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141449687368.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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