题目

如图所示为质谱仪的示意图．速度选择器部分的匀强电场场强E，匀强磁场的磁感应强度为B1；偏转分离器的磁感应强度为B2 ． 一质量为m，电荷量为+q的带电微粒进入速度选择器．不计带电微粒的重力．求： （1） 能通过速度选择器的粒子速度有多大？ （2） 微粒进入偏转分离器后，在磁场中运动的半径为多大？假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。错误涉及一个单词的增加、删除或修改。增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。删除：把多余的词用斜线( \ )划掉。修改：在错的词下面划一横线，并在该词下面写出修改后的词。注意：1. 每处错误及修改均仅限一词；2. 只允许修改10处，多者（从11处起）不计分；3. 错误类型不涉及单词拼写。Zhou Kai, a senior school student, is very fit. He takes a lot of exercises. He is crazy in football and is captain of the class team at school. His mother always make sure his family eat very healthy. Fresh fruit and vegetables are a very important part of their diet. Live near the sea, they often have fish. He is not too heavy, so he never has to diet, and anything like that. Zhou Kai is such healthy a boy that he rarely gets a cold or flu. But in last week, he fall ill. That was because he was stupid enough play football in the rain.