题目内容
在空间中水平面
的下方存在竖直向下的匀强电场,质量为
的带电小球由
上方的
点以一定初速度水平抛出,从
点进入电场,到达
点时速度方向恰好水平,
三点在同一直线上,且
,如右图所示.由此可见( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082415323707418847.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153235998513.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236138337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153235998513.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236310300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236419309.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236700313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236825512.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236965589.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082415323707418847.png)
A.电场力为![]() |
B.小球带正电 |
C.小球从A到B与从B到C的运动时间相等 |
D.小球从A到B与从B到C的速度变化量的大小不相等 |
A
试题分析:小球在MN上方做自由落体,根据题意在MN下方做类平抛运动。已知
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153236965589.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153237324594.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153237324594.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153237605598.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241532377301191.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153237823644.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153237901549.png)
点评:此类题型综合了平抛运动和类平抛运动规律(倒着运动),通过利用类平抛规律并结合运动独立性求解,属于要求较高的数理结合类题型。
![](http://thumb2018.1010pic.com/images/loading.gif)
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