题目

如图所示，长为L的细线的一端固定于O点，另一端系一质量为m的小球在水平拉力F作用下，小球以恒定速率在竖直平面内由最低点A运动到B点，OB与竖直方向成角在此过程中 A. 小球所受合外力一直增大B. 外力F一直增大C. 小球重力势能增大D. 拉力F做功为 答案：【答案】B【解析】抓住小球做匀速圆周运动，根据向心力的大小判断合外力的大小变化及F的变化，根据动能定理求拉力做功．A、因为小球做匀速圆周运动，合外力提供向心力，合外力大小不变，故A错误。B、小球从最低点向上运动的过程中，向上的分速度逐渐增大，所以克服重力做功的功率逐渐增大Indian's snake charmers are to be retrained as wildlife teachers under a plan to prevent their unique skills and knowledge from being lost. The charmers, who make snakes dance to the sound of flutes(笛子), used to be a traditional feature of Indian life, performing in towns and villages, until they were banned in 1972 to control the trade in snake skins. The government is now considering a plan to train the saperas, as they are known, to visit schools and zoos to tell children about forests and wildlife. There is also a proposal to set up a “dial a snake charmer” service to help householders to deal with unwelcome intruders. “For generations they have been a feature of Indian life but now they can't earn a living for fear of arrest,” said Behar Dutt, a conservationist behind the plans, “if a policeman doesn’t catch them, animal rights activists report them.” Many snake charmers have continued to work clandestinely since the ban, despite the threat of up to three years in jail. But their trademark cloth-covered baskets, hung from a bamboo pole carried across their shoulders, make them an easy target for police. The fate of Shisha Nath, 56, from Badarpur, a village just outside of Delhi, is typical of practitioners(从业者) of the dying art. “I used to earn enough to support my family and send my children to school,  "he said. "Now it's hard to earn even f, 1 a day. My children want to be snake charmers. It’s our identity. We love the work. But it s become impossible. Next month Dutt’s project to train 30 snake charmers will begin at a snake park in Pune, western India, where experts will enrich their home-grown skills with some formal knowledge. More than the law, though, it is the dishonest attitude of their fellow countryman that angers many snake charmers. "'We're disturbed all the time but when people want a snake removed from the house, they rush to us," said Prakash Nath, who was ordered recently to the home of Sonia Gandhi, the Congress party leader. 1.    According to the passage, snake charmers will be retrained as wildlife teachers mainly because___. A. schools need large numbers of such teachers B. most of them cannot support their families C. their performances on the street are banned D. the government plans to save the dying art 2.    The purpose of the proposed "dial a snake charmer" telephone service is ___. A. to give performance of snake dancing B. to teach householders how to catch and kill snakes C. to offer cleaning service to wealthy householders D. to help remove unwanted snakes from the houses 3.    The word "clandestinely" in paragraph 4 can be best replaced by the word "___" A. secretly            B. publicly            C. subconsciously               D. diligently 4.    Which of the following statements is NOT true according to the passage? A. Snake charmers can easily be recognized by the police on the street. B. Children of snake charmers would not like to continue their fathers' job. C. Snake charmers are quite angry with the attitude of their fellow countrymen. D. The animal rights activists take a negative attitude towards snake charmers.