问题 问答题 简答题

国际单位制中压力的单位是什么?它是如何定义的?它与工程大气压如何换算?

答案

参考答案:

国际单位制中压力的单位是帕斯卡,简称“帕”,其单位符号是Pa。

它的定义为:1牛顿力垂直且均匀地作用在1平方米的面积上所产生的压力。

因为1牛顿就是使1公斤质量的物体产生1米/秒2加速度的力。1公斤力是1公斤质量的物体在重力加速度为9.806565米/秒2时所表现的重力。因此1Kgf=9.806565N。

即:1Kgf/cm2=9.806565×104N/m2=0.980665×105Pa

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.

10()

A.Likewise

B.Moreover

C.However

D.Though