题目内容
如图所示,在O点处固定一正电荷,在过O点的竖直平面内的A点,自由释放一个带正电的小球,小球的质量为m、电荷量为q,小球下落的轨迹如图中虚线所示,它与以O为圆心、R为半径的圆(图中实线所示)相交于B、C两点,O、C在同一水平线上,∠BOC=30°,A距离OC的竖直高度为h,若小球通过B点的速度为v,则下列说法中正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250031521713250.png)
A.小球通过C点的速度大小是![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152187501.png)
B.小球通过C点的速度大小是![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152202571.png)
C.小球由A到C电场力做功是
mv2-mgh
D.小球由A到C机械能的损失是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250031521713250.png)
A.小球通过C点的速度大小是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152187501.png)
B.小球通过C点的速度大小是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152202571.png)
C.小球由A到C电场力做功是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152233286.png)
D.小球由A到C机械能的损失是
BD
试题分析:小球从A点到C点的过程中,电场力总体上做的是负功,重力做正功,由动能定理:mgh-W电=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152249713.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152280829.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250031522961157.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152311533.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152343829.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152358678.png)
由动能定理得mgh+W电=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152249713.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152233286.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003152233286.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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