题目

The day when I would go off to college was around the corner.Mom stood me in her usual spot behind the ironing board(烫衣板) and said，“Pay attention: I’m going to teach you to iron.”Mom clearly explained her ______ for this lesson.I was going to be ______ and needed to learn this _____ skill.Also，I would be meeting new people，and properly ironed clothes would help me make a good _____.“Learn to iron a shirt，” Mom said，“and you can iron _____.”But ironing shirts was not ______ work.It didn’t make use ______long muscles we used to throw a baseball，and it wasn’t a    设在地面上方的真空室内，存在匀强电场和匀强磁场。已知电场强度和磁感应强度的方向是相同的，电场强度的大小E=4.0V/m，磁感应强度的大小B=0.15T。今有一个带负电的质点以v=20m/s的速度在此区域内沿垂直场强方向做匀速直线运动。求此带电质点的电量与质量之比q/m以及磁场的所有可能方向(角度可用反三角函数表示)。