问题 选择题

如图所示为某质点做直线运动的v-t图象,关于这个质点在4s内的运动情况,下列说法中正确的是(  )

A.质点始终向同一方向运动

B.4s内通过的路程为4m,而位移为零

C.4s末物体离出发点最远

D.加速度大小不变,方向与初速度方向相同

答案

答案:B

题目分析:图象的斜率不变,因此物体做匀变速直线运动,开始时速度方向与加速度方向相反,物体减速运动,t=2s时,物体速度减为零,然后物体反向加速运动,t=4s时,回到起始点,由图可知物体所经历的路程为:,位移为零,B正确;

填空题
填空题

How many of us would temp for three years while we waited for the perfect job Not many of us, perhaps. But Wentworth Miller, the "Prison Break" star, said he chose to wait even longer time (1) he found the right job.
"Actually I think it might have been three or four years until I was lucky enough to get guest (2) on TV shows," said Miller, 34, who rose to international stardom (3) to "Prison Break" in 2006. That kind of patience and p will was portrayed in "Prison Break". Miller (4) engineering wizard Michael Scofield, who tries everything to break out of a Chicago (5) with his brother. Miller said he was fond of his character, (6) he said "exists in shades of grey".
Miller comes from a (7) of teachers. He said he didn’t seem fated for a career in the arts, (8) his passion for acting. After (9) from Princeton with an English degree, he moved (10) his parents’ request to Los Angeles to look for a stable life. He started (11) in a little company that made television movies. This (12) simply faxing, filing, walking the boss’ dog and going to the store for the boss’ lunch. Every weekend during the summer, Miller (13) go to the office (14) he didn’t have air-conditioning. "I would hang (15) in the conference room and set up camp and rob the company kitchen," recalled Miller.
(16) , Miller realized he still had questions about his choice. He decided to quit. But the boss said he was making a mistake and offered him a well-paid assistant position. "I eventually (17) that if I did the corporate job, it would be great if I was successful, but I would always wonder about the (18) . If I did the acting and was successful, I would never wonder (19) that job," he explained. He quit and temped (20) many people in the entertainment industry.
Now, he’s a hot star and has people coming up to him at film festivals saying, "Weren’t you the one who (21) to stand by the copy machine "
"That was tough, but I’m glad I have that perspective. Because now I’m at a point (22) big shots laugh at all my jokes and I think, You know, I got coffee for people like you for six years’. So I know what’s (23) , because I’ve seen the other side." But what if, when he was offered the corporate job, there had been more money "It was never about the (24) There’s a kind of excitement that comes along with acting. I can’t find it anywhere else. Even if I had to go back to temping, even if this is not the beginning of an amazing career, I would not (25) making that jum
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