如图所示,竖直放置的
、
两平行板间存在着水平向右的匀强电场
，、
间的距离为
，板上有一水平小孔
正对右侧竖直屏上的
点，以为坐标原点建立
坐标系
轴水平、
轴竖直)。板与屏之间距离为
，板与屏之间存在竖直向上的匀
强电场
和匀强磁场
。一个带正电的可视为质点的微粒从紧贴板右侧的
点以某一
初速度
竖直向上射出，恰好从小孔水平进入
右侧区域，并作匀速圆周运动，最终打在屏上的
处。已知微粒电量和质量的比值
，初
速度
，磁感应强度
，板与屏之
间距离，屏上点的坐标为(
)。
不考虑微粒对电场和磁场的影响，取
。求：
(1)匀强电场的大小；
(2)、间的距离的大小；
(3)微粒运动的总时问。
（1）
（2）
（3）
（1）微粒进入
板右侧区域，作匀速圆周运动得；
······················································································· 2分
································································· 2分
（2）微粒作匀速圆周运动的半径为
··········································································· 2分
由几何关系得：
································································· 2分
圆心角
·················································································· 2分
···················································································· 2分
····························································· 2分
微粒从A到
，竖直方向匀减速，水平方向匀加速
竖直方向：
············································ 2分
水平方向：························································· 2分
（3）匀速圆周运动的周期
·············································································· 2分
·········································································· 2分
（其他正确解法同样得分）