题目

(8分)一质量为10kg的物体在长为5m的绳子牵引下，在竖直平面内作圆周运动，通过最低的速度为10m/s，求此时对绳子的拉力。（g=10m/s2）  答案：300N解析:对物体在最低点处受力分析，得               -----5分代入数据得       -----3分 15．The survey by The Harvard Crimson was emailed to incoming first year undergraduates； 1，600 students responded．Results showed that at least a tenth of the students polled admitted to having cheated on an exam before starting at the university，while almost half admitted to cheating on their homework．Athletes were apparently the most prone to cheating.20 percent of students who played a university sport admitted to cheating on an exam compared to 9 percent of students who did not．The survey also revealed that men were not only more likely to cheat but were also more likely to admit to it．The results，compared to a previous survey done on the class of 2013，suggested that cheating may be becoming more commonplace．Of the outgoing seniors only 7 percent admitted to cheating in an exam and another 7 percent said they had been dishonest on a take-home test.32 percent of the seniors said they had cheated on homework during their undergraduate years．The surveys come in the wake of a cheating scandal at the university which saw 120 students investigated for sharing answers on an exam in 2012．One recent graduate stated："Cheating was commonplace when I was at Harvard，especially with students in their first year or two．I would say as many as 60 per cent of students took notes into some exams．No one really cared and the faculty，well some of them at least，seemed to recognize and yet ignore the problem"．In an email to NBC News，Jeff Neal，a Harvard representative，explained that a committee，made up of faculty，staff and students had been established to tacklecheating，which"is a national problem in American education"．63．Of the following 4 university students，who is most likely to cheat？AA．Jack，an athletic freshman   B．Rose，a second-year student C．John，a second-year student  D．Maria，a first-year student 64．According to para.4& 5，which of the following statement can be inferred？AA．They have done more than one survey．B．only 7% of the seniors have cheated in the exams．C．It seems more and more undergraduates are cheating．D．Students are more likely to cheat in their senior years．65．Why did The Harvard Crimson conduct the survey？DA．Because they want to wake up the cheating students．B．Because the faculty recognized and yet ignored the problem．C．Because cheating has become a more commonplace．D．Because there was a cheating scandal at the university．66．Which word has the closest meaning to the underlined word"tackle"in the last paragraph？CA．stop       B．punish     C．solve    D explain．