题目内容
如图所示,一个质量为m、电荷量为q的带正电的小球以速度v0沿水平光滑绝缘平面向右运动.在运动的正前方向有一垂直于纸面向里的匀强磁场,磁感应强度的大小为B,磁场左边有边界,右边无边界.当小球在磁场中离开平面向上升高h时,速度方向变为竖直向上,小球此时加速度的大小____________.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209530782935.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209530782935.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953094243.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953109841.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209531252927.jpg)
小球进入磁场,当它离开平面后只受重力和洛伦兹力作用,洛伦兹力不做功,机械能守恒,运动轨迹如图所示.设小球上升高度h时的加速度大小为a,有:
mv02=
mv2+mgh
F合=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953172618.gif)
解得:a=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953187388.gif)
=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953094243.gif)
.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953140225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953140225.gif)
F合=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953172618.gif)
解得:a=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953187388.gif)
=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953094243.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120953109841.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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