首页
登录
职称英语
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
游客
2023-07-27
62
管理
问题
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese children played with a fanlike toy that spun upwards and fell back to 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 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 airlines 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. [br] How can that helicopter work?
选项
答案
It works with the aid of a rotating device topside.
解析
同是第二段第一句指出了盲升机之所以能飞行是由于顶部安置了可以旋转的风扇。
转载请注明原文地址:https://tihaiku.com/zcyy/2873761.html
相关试题推荐
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Forcenturiesmendreamedofachievingverticalflight.In400ADChinesech
Forcenturiesmendreamedofachievingverticalflight.In400ADChinesech
Forcenturiesmendreamedofachievingverticalflight.In400ADChinesech
随机试题
Thewaypeopleholdtothebeliefthatafun-filled,painfreelifeequalsh
甲公司为一家在上海证券交易所上市的企业,主要从事电网调度、变电站、工业控制等自动
WhichAmericanuniversityiswiththelo
下列情形中,劳动者可以获得经济补偿的有()。A.用人单位被依法宣布破产而终止劳
女性,26岁,产前检查发现子宫肌瘤直径2cm。足月顺产后,阴道流血淋漓2月余,前
主要用于小儿的吸氧方法是()。A.鼻导管法 B.鼻塞法 C.面罩法 D.头
下列关于资本作用的说法,正确的有()。A.资本为商业银行提供融资 B.吸收
甲创作并出版的经典童话《大灰狼》超过著作财产权保护期后,乙将“大灰狼”文字及图形
管线测设时,其主点有()。A.起点 B.终点 C.窨井点 D.转折点 E
某有色金属材料在大气、淡水、海水中很稳定,对硫酸、磷酸、亚硫酸、铬酸和氢氟酸等有
最新回复
(
0
)