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问题 选择题

如图所示：一带电液滴在水平向左的匀强电场中由静止释放，液滴沿直线由b运动到d直线bd方向与竖直方向成45°角，则下列结论正确的是

A．液漓带正电荷

B．液滴的动能不变、

C．液滴做匀速直线运动

D．液滴的电势能减少

答案

答案：D

题目分析： 由题意可知，带电液滴只受重力和电场力作用，两个力都是恒力，其合力沿bd方向，则电场力必定水平向右，故液滴带负电荷，做匀加速直线运动；合力做正功，据动能定理知，动能增大；电场力对液滴做正功，液滴的电势能减少，故D正确．

填空题

Of all the employed workers in the United States, 12.5 million are part of a temporary workforce. The United States Bureau of Labor Statistics counts 9.2 percent of workers as those who have______(1) they term "alternative employment arrangements." The government predicts that temporary staffing agencies______(2) experience growth of 49 percent by 2010. If numbers increase at the rate ______ (3), these companies will add 1.9 million new jobs by 2010. That’’s more than any______(4) industry.Temporary workers were the first ones to be affected by the recent economic recession, but they are______(5) to be the first to regain positions as the economy picks up and companies work to rebuild. Employers use temporary workers as a resource because_______(6) offer flexibility and come at a low cost. Many temporaries are categorized as "independent contractors" instead of employees,______(7) allows the employer to avoid______(8) certain taxes. Because they are not required to offer benefits to temporary workers, companies can save a great deal of money by hiring temps. Usually, temporary workers can qualify_______(9) benefits if they work for a staffing company for a certain length of time. Most temps, however, do not continue with one company long______(10) to qualify for them because they regard the position as a step on the ladder to a______(11) position later.According to Richard Wahlquist, president of the American Staffing Association, 75_______(12) of temporary workers hope for transition out of the temporary staffing category______(13) a period of time. Wahlquist finds that temporary workers spend about 11 weeks on various assignments before their______(14) out of the temporary workforce. Many use temporary positions to gain experience and skills______(15) they move on to better jobs. Wahlquist says that the temp workforce as a whole turns______(16) 400 percent each year.Tom Dilworth, research director at the Employment Policies Institute, explains______(17) some workers like having temporary jobs______(18) it affords them a great deal of elasticity with time and everything. Some temps only have a limited______(19) of time to work and temp agencies can help coordinate jobs to fit their schedules. Other sometimes-employees use temporary jobs to get an______(20) to a company from the inside, to get a foot in the door of a certain business or career._______(21) others take temporary positions in hopes their employers will change them over to permanent positions eventually.Nearly all the industries in the United States use temporary workers.______(22) to Tim Costello, coordinator of the North American Alliance for Fair Employment, the growth of temporary labor threatens______(23) job security of permanent workers who fear replacement, as well as the temps who are more accustomed to turnover. He predicts that there will continue to______(24) a gradual shift from permanent employees to contingent staffing, and that such a_____(25) in workplace demographics will "lead to lower wages, poorer working conditions, and more instability."
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单项选择题

古希腊哲学家伊壁鸠鲁致美诺寇的信中写道：“当一个人年轻的时候，不要让他耽误了哲学研究，当他年老的时候，也不要让他对它的研究产生厌倦，因为要获得灵魂的健康，谁也不会有太早或太晚的问题。”这说明哲学（）

A.研究人的精神世界，使人获得精神上的满足

B.能指导人们正确地认识世界和改造世界

C.是指导人们生活得更好的艺术

D.产生于人类的实践活动和人们对实践的追问
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