题目内容
如图所示,Ox、Oy、Oz为相互垂直的坐标轴,Oy轴为竖直方向,整个空间存在竖直向下的匀强磁场,磁感应强度大小为B.现有一质量为m、电量为q的小球从坐标原点O以速度v0沿Ox轴正方向抛出(不计空气阻力,重力加速度为g).求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038292852508.jpg)
(1)若在整个空间加一匀强电场E1,使小球在xOz平面内做匀速圆周运动,求场强E1;
(2)若在整个空间加一匀强电场E2,使小球沿Ox轴做匀速直线运动,求E2的大小;
(3)若在整个空间加一沿y轴正方向的匀强电场E3,使E3=3E1,求该小球从坐标原点O抛出后,经过y轴时的坐标y的表达式.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038292852508.jpg)
(1)若在整个空间加一匀强电场E1,使小球在xOz平面内做匀速圆周运动,求场强E1;
(2)若在整个空间加一匀强电场E2,使小球沿Ox轴做匀速直线运动,求E2的大小;
(3)若在整个空间加一沿y轴正方向的匀强电场E3,使E3=3E1,求该小球从坐标原点O抛出后,经过y轴时的坐标y的表达式.
(1)
方向沿y轴正向 (2)
(3)y=
(n=1,2,3……)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829316528.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038293321056.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829348947.png)
试题分析:(1)由于小球在磁场中做匀速圆周运动,设轨道半径为r,则
qE1=mg解得E1=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829316528.png)
方向沿y轴正向 (1分)
(2)小球做匀速直线运动,受力平衡,则
qE2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829379976.png)
解得E2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250038293321056.png)
(3)小球在复合场中做螺旋运动,可以分解成水平面内的匀速圆周运动和沿y轴方向的匀加速运动.
做匀加速运动的加速度a=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829410723.png)
从原点O到经过y轴时经历的时间t=nT=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829426736.png)
y=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829441338.png)
解得y=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003829348947.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目