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
49
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
Moreandmoreemployersusetheonlineapplicationprocesstohelpthemfindtherightpersonforthejob.So,it’slikelythat
(英语专业学生做)Ineverycultivatedlanguagetherearetwogreatclassesofwordswhich,takentogether,comprisethewholevocabu
ItissoexpensivethatIcan’t______it.
Nearlytwothousandyearshavepassed______theChinesefirstinventedthecompass.
(非英语专业做)Increasinglyoverthepast10years,Peopleespeciallyyoungpeoplehavebecomeawareoftheneedtochangetheire
You’dthinkPaulineHordwouldhaveservedhertimebynow.Afterall,sherecentlycelebratedher90thbirthday,andbytheti
Crimeisincreasingworldwide,andthereiseveryreasontobelievethe______willcontinueintothenextdecade.
You______himatthepartylastnight.Isawhimoffattheairportyesterdayafternoon.
随机试题
阴道自净作用主要得益于
在我国,香港特别行政区依法享有的权利包括:
在履行建设工程设计合同过程中,双方发生争议,以下解决方式中不正确的是()
可行性研究综合研究建设项目的()。
某上市公司董事吴某,持有该公司6%的股份。吴某将其持有的该公司股票在买入后的第5个月卖出,获利600万元。根据证券法律制度的规定,关于此收益,下列表述中,不正确的是()。
指出“大学者,非谓有大楼之谓也”的教育家是()。
①自恋型人格:指过于重视自我价值而缺乏对自身和他人进行理性和客观认识的一种人格。②回避型人格:指行为退缩、心理自卑,面对挑战多采取回避态度或无能应付的一种人格。③强迫型人格:指过于要求严格和完善,具有强烈的自制心理和自控行为的一种人格。
根据以下资料。回答下列题。2008年主要国家(地区)货物出口额之和占世界货物出口总额的比重是2005年的()倍。
秋收起义
设A,B为n阶矩阵,|λE-A|=|λE-B|且A,B都可相似对角化,证明:A~B.
最新回复
(
0
)