t=l/Vo qE=ma
v'=qul/(mdVo)
(1).y=½at²=qul²/(2mdVo²)
(2)Eq=qBVo E=u/d
B的大小:B=u/(d Vo) 指向纸面
(3) qBv- qE=ma' a'=(qBv-qE)/m