一质点沿直线Ox方向做变速运动,它离开O点的距离x随时间变化的关系为x=5+2t3(

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问题:

一质点沿直线Ox方向做变速运动,它离开O点的距离x随时间变化的关系为x=5+2t3(m),它的速度随时间t变化的关系为v=6t2(m/s),该质点在t=0到t=2s间的平均速度和t=2s末的瞬时速度的大小分别为()

A.12m/s,24m/s

B.8m/s,24m/s

C.12m/s,19.5m/s

D.8m/s,13m/s

考点:高中物理匀变速直线运动基本公式应用匀变速直线运动基本公式应用题库
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鲍照,字明远,世称()。他擅长写()言歌行,能够吸收民歌的精华,情感(),语言(),形象鲜明。

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农业上对农作物进行合理密植主要是为提高作物对土壤中肥料的利用率.______.

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A total of 4.6 million digital televisions have been sold, and the sales of HDTV sets have quadrupled since last year. Consumers have bought HDTVs to play their DVDs and to have clearer pictures and wide screens. Only a small percentage of the people who have purchased HDTVs, however, have actually hooked their TVs up to receive high-definition television digital signals. Perhaps television viewers are having trouble keeping up with the changes in technology. Even the manufacturers of HDTVs, like Mitsubishi, Thomson Multimedia, Sony, and Samsung seem to have a tough time learning how to make their sets work with the various digital TV formats because little standardization has been required or implemented in the industry.
Some of the HDTVs Weigh over 200 lbs., and a variety of retailers offer a delivery service to the buyer’s home to help install the heavy sets. This is known as a white-glove service and usually comes with an extra fee. After HDTV purchasers get their sets home and hook them up, they will still need to Work to get the digital signals to their systems. Most of the industry’s cable providers do not yet offer high-definition programing, and only about 15% of commercial television stations have switched over to even the lowest improved digital pictures. Worse yet, viewers may need to install antenna before they can even get the digital signals to their new HDTV sets. Another frustration for home-theater seekers is that the current HDTV sets allow owners only to watch high-definition programs, not to record them.

"Hook up" as in "hooked their TVs up" underlined in Paragraph 1. most probably means to______.

A.have a hood over the TV

B.be connected to

C.relate oneself to

D.keep contact with

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遗传性疾病可分为()

A.染色体病

B.单基因遗传病

C.多基因遗传病

D.线粒体遗传病

E.DNA突变遗传病

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对环境影响很小的建设项目,应编制( )。

A.环境影响报告书
B.重大环境影响因素统计汇总表
C.环境影响报告表
D.环境影响登记表

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