题目

Is there a strange something high up in the world’s tallest mountains?If so,is a big bear?Is it a monkey? Or is it a kind of man? No one knows. This mystery has puzzled the world for years. In 1887, a mountain climber found large footprints in the snow. They looked like the footprints of a very large man .But men don’t walk without shoes in the snow! In 1906, another climber saw more than footprints. Far off, he saw a very large animal standing on two legs. As he watched, it was running very quickly. Fifteen years later, newspapers had new stories about the “something”.A mounta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)