问题 选择题

图甲为一列简谐横波在t=0.10s时刻的波形图,P是平衡位置为x=1m处的质点,Q是平衡位置为x="4" m处的质点,图乙为质点Q的振动图象,则                             

A.t=0.10s时,质点Q的速度方向向上

B.该波沿x轴负方向的传播,传播速度为40m/s

C.再经过0.10s,质点Q沿波的传播方向移动4m

D.从t=0.10s到t=0.25s,质点P通过的路程为30 cm

答案

BD

由乙图找到t=0.10s时,质点O向下振动,A错;结合甲图,能判断这列波向左传播,波长为8m,周期为0.2s,波速v=λ/T=40m/s,质点不随波迁移,C错;从t=0.10s到t=0.25s,质点P振动四分之三个周期,振动的路程为3A=30cm

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.

2()

A.dwell

B.rely

C.press

D.urge