题目内容
如图所示,质量为m、电荷量为q的带电粒子,以初速度v0垂直射入场强为E,方向竖直向下的匀强电场中,该粒子在电场中的经历时间_____后,其即时速度的方向与初速度方向成30º角.在这过程中粒子的电势能增量为_______.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602240882.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602240882.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602286806.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602302657.png)
即时速度的方向与初速度方向成30º角,则竖直速度
,该粒子在电场中做类平抛运动,所以
,则可知该粒子在电场中的经历时间t=
,根据动能定理可知,在这过程中粒子的电势能减少,减少量等于动能的增加量,即时速度
,则有![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316026301295.png)
故答案为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602302657.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316023331013.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316025361118.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602286806.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316025981018.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241316026301295.png)
故答案为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602286806.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131602302657.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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