题目内容
静止在匀强磁场中的
Li核俘获一个运动方向垂直于磁场,速度大小为v0=7.7×104m/s的中子,发生核反应
Li+
n→
H+
He。若已知
He核的速度大小为vt=2.0×104m/s,方向与反应前中子的速度方向相同,求:
(1)
H核的速度;
(2)
H核与
He核在磁场中做匀速圆周运动的半径之比;
(3)当
H核旋转3周时,
He核旋转几周?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114629980217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114629980217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630136217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
(3)当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
(1)
,与中子的运动方向相反
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630495372.gif)
(3)2周
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630479336.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630495372.gif)
(3)2周
(1)由动量守恒定律,有mnvp=mHev1+mHv2
解得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630511620.gif)
H核的速度大小为1.0×103m/s,方向与中子的运动方向相反.
(2)粒子做匀速圆周运动的半径为R 由
对
H核,
对
He核,
代入数值解得
(3)粒子做匀速圆周运动的周期为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630651349.gif)
对
H核,
对
He核,
代入数值解得:
所以,当
H核旋转3周时,
He核旋转2周
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630511620.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
(2)粒子做匀速圆周运动的半径为R 由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630557533.gif)
对
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630589406.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630620421.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630495372.gif)
(3)粒子做匀速圆周运动的周期为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630651349.gif)
对
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630682381.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630713425.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630729341.gif)
所以,当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630167213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114630183218.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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