首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
专升本
For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese children played with a fan-like toy that spun upwar
For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese children played with a fan-like toy that spun upwar
admin
2014-06-25
79
问题
For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese children played with a fan-like toy that spun upwards and fell back to earth as rotation ceased. Leonardo da Vinci conceive the first mechanical apparatus, called a "Helix," which could carry man straight up, but was only a design and was never tested.
The ancient-dream was finally realized in 1940 when a Russian engineer piloted a strange looking craft of steel tubing with a rotating fan on top. It rose awkwardly and vertically into the air from a standing start, hovered a few feet above the ground, went sideways and backwards, and then settled back to earth. The vehicle was called a helicopter.
Imaginations were fired. Men dreamed of going to work in their own personal helicopters. People anticipate that vertical flight transports would carry millions of passengers as do the airliners of today. Such fantastic expectations were not fulfilled.
The helicopter has now become an extremely useful machine. It excels in military missions, carrying troops, guns and strategic instruments where other aircraft cannot go. Corporations use them as airborne offices, many metropolitan areas use them in police work, construction and logging companies employ them in various advantageous ways, engineers use them for site selection and surveying, and oil companies use them as the best way to make offshore and remote work stations accessible to crews and supplies. Any urgent mission to a hard-to-get-to place is a likely task for a helicopter. Among their other multitude of uses: deliver people across town, fly to and from airports, assist in rescue work, and aid in the search for missing or wanted persons.
Helicopters work with the aid of______.
选项
A、a combination of rotating devices in front and on top
B、a rotating device topside
C、one rotating fan in the center of the aircraft and others at each end
D、a rotating fan underneath for lifting
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/XXUC777K
本试题收录于:
英语题库普高专升本分类
0
英语
普高专升本
相关试题推荐
Manychangesaretakingplacein"foodstyle"intheUnitedStates.TheUnitedStatesistraditionallyfamous【36】itsverysolid
Manychangesaretakingplacein"foodstyle"intheUnitedStates.TheUnitedStatesistraditionallyfamous【36】itsverysolid
Itis______onethousandstudentscanliveinit.
______childrenhavebeentakenoutofschoolandtaughtbytheirparentsathome.
Haveyou【56】askedyourselfwhychildrengotoschool?Youwillprobablysaythattheygo【57】languages,mathematics,history,sci
Theheatingsystemhasrecentlybeen______tomakeitmoreefficient.
Allfactors______,theybegantodosomethingaboutthesituation.
ForanincreasingnumberofstudentsatAmericanuniversities,Oldissuddenlyin.Thereasonisobvious:thegrayingofAmerica
(2007)Thereisashortageofparkingspace;______parkingisbecomingmoreexpensive.
随机试题
学校、职业群体、社团等属于【】
决定和影响劳动生产率高低的因素主要有()。
决定是否与另一个组织合并,如何重组以提高效率,或是否关闭一个亏损的工厂,这些都是典型的()
羊水过少
所谓潜伏期是指
甲与乙一起进城办事,由甲驾车回家,乙坐在后排座位上,甲经过一路口,突然闯红灯,撞上经过此路口的行人丙,乙见状对甲说:“赶紧走,现在没有人看见。”甲加大油门,狂奔5公里。丙因得不到及时的救助而不幸身亡。甲因交通肇事被依法逮捕,请问此时乙的行为如何认定?
根据《环境影响评价技术导则大气环境》(HJ2.2—2008),可用于预测评价范嗣大于50km影响的模式系统是()。
在冬季,人们往往容易鼻子出血,因而常常在房间的地上洒一些水,或在室内放一盆清水、挂一些湿毛巾等。对以上做法最合理的解释是()。
导游人员在讲解时要正确掌握语音、语气和语调,既要有鲜明生动的语言,又要注意语言的音乐性和节奏感。这说明导游讲解应()。
西方发达国家职业道德建设的主要经验是()
最新回复
(
0
)