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问题 单项选择题

一个小石子从某一楼房顶由静止自由落下，某摄影爱好者恰好拍到了它下落的一段轨迹AB。该爱好者用直尺量出轨迹的实际长度，如图所示。已知拍摄时所用照相机的曝光时间为0.01s，（g取10m/s2），则小石子通过B时速度为（）

A.2.00m/s

B.2.15m/s

C.2.05m/s

D.2.25m/s

答案

参考答案：C

解析：

匀变速直线运动过程中一段位移内的平均速度等于该段位移的中间时刻速度，故，故根据速度时间公式可得：，故C正确

多选题

甲物体的重力比乙物体的重力大5倍，甲从H m高处自由落下，乙从2H m高处同时自由落下（设高度足够高）。则说法正确的是[ ]

A．两物体下落过程中，同一时刻甲的速率比乙大

B．下落l s末，它们的速度相等

C．各自下落l m它们的速度相等

D．下落过程中甲的加速度比乙大

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单项选择题

You’re busy filling out the application form for a position you really need, let’s assume you once actually completed a couple of years of college work or even that you completed your degree. Isn’t it tempting to lie just a little, to claim on the form that your diploma represents a Harvard degree Or that you finished an extra couple of years back at State University
More and more people are turning to utter deception like this to land their job or to move ahead in their careers, for personnel officers, like most Americans, value degrees from famous schools. A job applicant may have a good education anyway, but he or she assumes that chances of being hired are better with a diploma from a well-known university. Registrars at most well-known colleges say they deal with deceitful claims like these at the rate of about one per week.
Personnel officers do check up on degrees listed on application forms, then. If it turns out that an applicant is lying, most colleges are reluctant to accuse the applicant directly. One Ivy League school calls them "impostors". Another refers to them as "special cases". One well-known West Coast school, in perhaps the most delicate phrase of all, says that these claims are made by "no such people".
To avoid complete lies, some job-seekers claim that they "attended" or "were associated with" a college or university. After carefully checking, a personnel officer may discover that "attending" means being dismissed after one semester. It may be that "being associated with" a college means that the job-seeker visited his younger brother for a football weekend. One school that keeps records of false claims says that the practice dates back at least to the turn of the century--that’s when they began keeping records, anyhow.
If you don’t want to lie or even stretch the truth, there are companies that will sell you a fake diploma. One company, with officers in New York and on the West Coast, will put your name on a diploma from any number of nonexistent colleges. The price begins at around twenty dollars for a diploma from "Smoot State University". The prices increase rapidly for a degree from the "University of Purdue". As there is no Smoot State and the real school in Indiana is properly called Purdue University, the prices seems rather high for one sheet of paper.

The main idea of this passage is that ______.

A. employers are checking more closely on applicants now
B. lying about college degrees has become a widespread problem
C. college degrees can now be purchased easily
D. employers are no longer interested in college degrees
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