题目内容
(10分) 如下图所示,质量为m=1kg,电荷量为q=5×10-2 C的带正电的小滑块,从半径为R=0.4m的光滑绝缘
圆孤轨道上由静止自A端滑下.整个装置处在方向互相垂直的匀强电场与匀强磁场中.已知E=100 V/m,水平向右;B=1T,方向垂直纸面向里.求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029003292.jpg)
(1)滑块到达C点时的速度;
(2)在C点时滑块对轨道的压力.(g=10 m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002702884303.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029003292.jpg)
(1)滑块到达C点时的速度;
(2)在C点时滑块对轨道的压力.(g=10 m/s2)
(1)
(2)20.1 N
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029151213.png)
试题分析:(1)滑块滑动过程中洛伦兹力不做功,由动能定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029151023.png)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029151213.png)
(2)在C点,受到四个力作用,如右图所示,由牛顿第二定律与圆周运动知识得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029623985.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029621095.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027029781414.png)
由牛顿第三定律可知,滑块对轨道的压力为20.1 N(1分)
![](http://thumb2018.1010pic.com/images/loading.gif)
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