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
外语
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
2010-03-26
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 the earth as rotation ceased. Leonardo da Vinci conceived the first mechanical apparatus, called a "Helix", which could carry a man straight up, but this 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 the earth. That vehicle was called a helicopter.
Imaginations were fired. Men dreamed of going to work in their own personal helicopters. People anticipated 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 are set to motion by means of______.
选项
A、one rotating fan in the centre of the aircraft and others at each end
B、a rotating fan underneath for lifting
C、a rotating device on top
D、a combination of rotating devices in front and on top
答案
C
解析
根据文章中第二段第一句话可知:直升飞机是通过安装在其顶部的螺旋桨启动的。因此,正确答案是C项。
转载请注明原文地址:https://kaotiyun.com/show/rXk7777K
0
大学英语四级
相关试题推荐
Whymoreandmorepeoplebecameinterestedinbecomingcomputerprogrammers?Whichisnotmentionedasthecharacteristicsofp
ThelargemajorityofBritishpeopletendto______.Whatdoesthispassagemainlytalkabout?
ThelargemajorityofBritishpeopletendto______.Britishpeopleareinfavourofbecomingmembersofvariousclubsinthat
RuthAnnandRobertLipicknewtheirchildrencouldmakemistakesthatcouldlastalifetime—maybeevenshortenalifetime.Asf
Duringtelevision’sfirst20years,deafpeoplemissedmostofthefunbecausethey______."closedcaptions"arecaptionsthat
Duringtelevision’sfirst20years,deafpeoplemissedmostofthefunbecausethey______."opencaptions"arecaptionsthat_
Duringtelevision’sfirst20years,deafpeoplemissedmostofthefunbecausethey______.Adecoderisamachineto______.
Ifyouwanttostayyoung,sitdownandhaveagoodthink.ThisistheresearchfindingofateamofJapanesedoctors,whosayt
A、Three.B、Four.C、Five.D、Six.DHowmanychildrenarethereinthewoman’sfamily?
A、Hedrivestoofast.B、Heplayshisguitartooloudly.C、Hisradiowakesherchildrenup.D、Hisfriendsaretoonoisy.CWhatbo
随机试题
足部斜方肌反射区适应症包括颈肩酸痛。()
女,26岁。在医院行拔牙术,注射麻药时,患者出现头晕,恶心,胸闷,四肢无力,查:血压90/60mmHg,脉搏65次/分,面部及口唇苍白诊断是
( )包括会议主持人,会议纪要的起草和会签,会议的主要内容,以及有关组织专题会议的要求。
混凝土有()等特点。
个人汽车贷款贷前调查可以采取的方式有()。
Excel中“撤销”操作只能撤销最近一次操作。()
下列关于中共七大的说法中,正确的是()。
患者,男性,34岁。右上6死髓、劈裂,要求拔除。拔除时应采用的麻醉包括()。
HighfieldHouseisneartheseaside.ThecurrentinhabitantsbelongtotheHighfieldfamily.
Geographyisstudyoftherelationshipbetweenpeopleandtheland.Geographerscompareandcontrast【C1】______placesontheea
最新回复
(
0
)