题目内容
(18分)如图所示为利用电磁作用输送非导电液体装置的示意图。一边长为L、截面为正方形的塑料管道水平放置,其右端面上有一截面积为S的小喷口,喷口离地的高度为h,管道中有一绝缘活塞,在活塞的中部嵌有金属棒,整个装置放在竖直向上的匀强磁场中,当棒中通有垂直纸面向里的恒定电流I时,活塞以某一速度向右匀速推动液体,液体以不变的速度v源源不断地沿水平方向射出。若液体的密度为ρ,重力加速度为g,不计所有阻力。求
(1)液体落地点离喷口的水平距离x;
(2)该装置的功率;
(3)磁感应强度B的大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500392918910196.png)
(1)液体落地点离喷口的水平距离x;
(2)该装置的功率;
(3)磁感应强度B的大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500392918910196.png)
(1)
;(2)
;(3)
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929221738.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039292361057.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039292521045.png)
试题分析:(1)液体喷出后做平抛运动
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929267636.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929299420.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929221738.png)
(2)设活塞运动速度v0
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929330573.png)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929361632.png)
设在时间t内有质量为△m的液体从喷口射出
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929377681.png)
时间t内装置对△m做功
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929392989.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039292361057.png)
(3)金属棒在磁场中受力
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003929486491.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039295011193.png)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250039292521045.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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