题目内容
(1)磁感强度B的大小。
(2)小球对轨道最低点的最大压力。
(3)若要小球在圆形轨道内作完整的圆周运动,小球从轨道的水平直径的M端下滑的最小速度。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153228352583.gif)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153228512093.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322866463.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322882791.gif)
(1)设小球向右通过最低时的速率为,据题有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153228972866.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322913354.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322929141.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322944344.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322960145.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322975341.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322960145.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323007341.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323022111.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322913354.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322929141.gif)
(2)小球向左通过最低点时对轨道的压力最大
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323069675.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322866463.gif)
(3)要小球完成圆周运动的条件是在最高点满足:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323100611.gif)
又因从M点到最高点据动能定理有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323116860.gif)
由以上可得![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322882791.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241153228972866.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322913354.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322929141.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322944344.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322960145.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322975341.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322960145.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323007341.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323022111.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322913354.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322929141.gif)
(2)小球向左通过最低点时对轨道的压力最大
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323069675.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322866463.gif)
(3)要小球完成圆周运动的条件是在最高点满足:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323100611.gif)
又因从M点到最高点据动能定理有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115323116860.gif)
由以上可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115322882791.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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