题目内容
质量为m,电量为+q的小球以初速度
以与水平方向成θ角射出,如图所示,如果在初速度所在的竖直平面加上一定大小的匀强电场后,能保证小球仍沿
方向做直线运动,则下列说法错误的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250025201423752.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520095322.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520095322.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250025201423752.png)
A.若小球做匀速直线运动,所加电场的值为![]() |
B.若小球做往返运动,所加匀强电场的值可能为![]() |
C.若小球做往返运动,所加匀强电场的值为![]() |
D.若小球做方向不变的匀加速运动,所加匀强电场的值应大于![]() |
C
试题分析:若小球做匀速运动,说明电场力和重力合力为零,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520361588.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520376660.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520392745.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520423852.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520439610.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002520454672.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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