题目

在电场强度为E的匀强电场中，有一条与电场线平行的几何线，如图中虚线所示，几何线上有两个静止的小球A和B（均可看做质点），两小球的质量均为m，A球带电荷量＋Q，B球不带电，开始时两球相距L，在电场力的作用下，A球开始沿直线运动，并与B球发生对碰撞，碰撞中A、B两球的总动能无损失，设在各次碰撞过程中，A、B两球间无电量转移，且不考虑重力及两球间的万有引力，问： (1)A球经过多长时间与B球发生第一次碰撞？ (2)第一次碰撞后，A、B两Just what is a tiger mother? Amy Chua is a law professor at America’s Yale University and her recent book on the subject is making waves. She’s been called “dangerous”，“outrageous”，even a “monster” for her descriptions of how she brought up her two daughters.Her book Battle Hymn of the Tiger Mother describes fighting with a daughter for hours at the piano to ensure the child gets a piece of music right. She rejected birthday cards made for her by her girls because she didn’t think they had made enough effort. She compared one child negatively with the other, threatening to burn their toys. Her rules include: schoolwork always comes first; an A-minus is a bad grade; children must be two years ahead of their classmates in math, and playing the violin or the piano is a must. Ms. Chua considers the Chinese hard work ethic as a way of creating happy, successful children—at least in her case. Although she’s had a large amount of flak for her theories, one thing can’t be ignored—the success of Chinese children in the education system.In Britain, shocking research shows that Chinese girls, for example, are outperforming all other foreign groups at GCSE—79 percent getting 5 A—C Grades, compared with 58 percent of white British girls. So what is it about Chinese parenting that’s leading to high achievers? And how do Amy Chua’s theories play into that success?She told me that if her daughter came back from school with 96/100 in a test, Chua would ask her what happened to the other 4 points. It’s about always knowing “you can do better”，she told me. Interestingly, in China, the birthplace of the tiger mother, people are moving away from traditional Chinese parenting. They are following more western parenting styles.1.What can we learn about Amy Chua according to Paragraph 2?A．She is very strict with her children.B．She doesn’t think her children are clever.C．She is very interested in playing the piano.D．She knows playing is important to children.2.The underlined word “flak” in the third paragraph probably means“________”．A．attentionB．criticismC．curiosityD．contribution3.It can be inferred from the text that ________.A．Amy Chua will change her methodsB．Amy Chua considers her methods usefulC．Amy Chua’s children don’t love their motherD．Amy Chua’s children prefer western parenting styles