题目内容
(15分))如图所示,电容为C、带电量为Q、极板间距为d的电容器固定在绝缘底座上,两板竖直放置,总质量为M,整个装置静止在光滑水平面上。在电容器右板上有一小孔,一质量为m、带电量为+q的弹丸以速度v0从小孔水平射入电容器中(不计弹丸重力,设电容器周围电场强度为零),弹丸未与左板相碰,最远可到达距右板为x的P点,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241219403103577.jpg)
(1)弹丸在电容器中受到的电场力的
大小;
(2)x的值;
(3)当弹丸到达P点时,电容器已移动的距离s。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241219403103577.jpg)
(1)弹丸在电容器中受到的电场力的
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412194032572.gif)
(2)x的值;
(3)当弹丸到达P点时,电容器已移动的距离s。
(1)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940341474.gif)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940357841.gif)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940372786.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940341474.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940357841.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940372786.gif)
(1)电容极板电压
………1分
极板问场强
………2分
则弹丸在电容器中受到的电场力的大小为
………2分
(2)弹丸到达P点时两者有共同速度,设为v,由动量守恒有:
………2分
对弹丸和装置,由功能关系得:
………2分
解得
………2分
(3)对装置,由动能定理得:
………2分
解得
………2分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940372412.gif)
极板问场强
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940403453.gif)
则弹丸在电容器中受到的电场力的大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940497552.gif)
(2)弹丸到达P点时两者有共同速度,设为v,由动量守恒有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940513550.gif)
对弹丸和装置,由功能关系得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940513665.gif)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940357841.gif)
(3)对装置,由动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940544567.gif)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121940372786.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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