题目

Social media is a big part of most people’s lives. There are social apps and sites like WeChat and Sina Weibo, as well as video apps like Douyin and Kuaishou. Recently scientists at the University of Sussex, UK, studied social media users from 10 to 15 years old. They found that they can be divided into four personality types.【1】There aretypes of people in this passage.A. three B. four C. five【2】Tony is a famous person on the Internet, maybe he likes tomost.A. use unreal names B. share his breakfast online C. share websites【3】What can we do to avoid being hurt by criminals?A. Kee如图所示，一质量为m，带电荷量为+q的粒子以速度从O点沿y轴正方向射入磁感应强度为B的圆形匀强磁场区域，磁场方向垂直纸面向外，粒子飞出磁场区域后，从点b处穿过x轴，速度方向与x轴正方向的夹角为30°，同时进入场强为E、方向沿x轴负方向成60°角斜向下的匀强电场中，通过了b点正下方的c点，如图所示．粒子的重力不计，试求： ⑴圆形匀强磁场的最小面积． ⑵粒子在磁场中运动的时间. ⑶c点到b点的距离d．