题目

根据短文内容，从方框中选择恰当的词语填空，有的需要变换形式probably, be, foreign, possible, look for, doctor, physical, hobby, able, grow upI knew a girl called Alice one year ago. She's a(n)     girl When she was small, she wasn't in good     condition (状况). She had a strange disease (怪病). Her parents took her to many hospitals. The     didn't know what happened to her.Now Alice     She's fifteen years old She isn't     to see or hear clearly. But she is a happy girl. She says to her（14分）如图甲所示，在水平放置的两平行金属板的右侧存在着有界的匀强磁场，磁场方向垂直于纸面向里，磁场边界和与平行板的中线垂直。金属板的两极板间的电压，匀强磁场的磁感应强度。现有带正电的粒子以的速度沿两板间的中线连续进入电场，恰能从平行金属板边缘穿越电场射入磁场。已知带电粒子的比荷，粒子的重力和粒子间相互作用力均可以忽略不计(结果保留两位有效数字)。(1)求射入电场的带电粒子射出电场时速度的大小和方向。(2)为使射入电场的带电粒子不会由磁场右边界射出，该匀强磁场区的宽度至少为多大?