问题 选择题

如图所示,为甲、乙两辆汽车从同一点、同时沿平直公路出发的s一t图象,从图象中可知

A.t1时刻,两车速度方向相同

B.t1时刻,两车速度大小相等

C.在t1时间内,两车的路程相等

D.在t1时间内,两车的平均速度相同

答案

答案:D

位移时间图像中倾斜直线的斜率正负表示速度方向,A错;斜率大小表示速度大小,B错;甲做的是往复运动,路程较大,C错;平均速度等于位移与时间的比值,位移相同,运动时间相同,所以平均速度相同,D对;

单项选择题
单项选择题

Although there are many skillful Braille readers, thousands of other blind people find it difficult to learn that system. They are thereby shut (1) from the world of books and newspapers, having to (2) on friends to read aloud to them.

A young scientist named Raymond Kurzweil has now designed a computer which is a major (3) in providing aid to the (4) .His machine, Cyclops, has a camera that (5) any page, interprets the print into sounds, and then delivers them orally in a robot-like (6) through a speaker. By pressing the appropriate buttons (7) Cyclops’s keyboard, a blind person can "read" any (8) document in the English language.

This remarkable invention represents a tremendous (9) forward in the education of the handicapped. At present, Cyclops costs $ 50,000. (10) , Mr. Kurzweil and his associates are preparing a smaller (11) improved version that will sell (12) less than half that price. Within a few years, Kurzweil (13) the price range will be low enough for every school and library to (14) one. Michael Hingson, Director of the National Federation for the Blind, hopes that (15) will be able to buy home (16) of Cyclops for the price of a good television set.

Mr. Hingson’s organization purchased five machines and is now testing them in Maryland, Colorado, Iowa, California, and New York. Blind people have been (17) in those tests, making lots of (18) suggestions to the engineers who helped to produce Cyclops.

"This is the first time that blind people have ever done individual studies (19) a product was put on the market," Hingson said. "Most manufacturers believed that having the blind help the blind was like telling disabled people to teach other disabled people. In that (20) , the manufacturers have been the blind ones.

16()

A.models

B.modes

C.cases

D.collections