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
34
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
Decidewhichofthechoicesgivenbelowwouldbestcompletethepassageifi
下列设计措施中,哪一条对于控制建筑物体型系数是不利的?()A.平面空间尽量减
对公司银行贷款逾期的罚息,正确的财务或税务处理是( )。A.罚息属于企业所得税法
腹腔镜胃、十二指肠溃疡穿孔修补术的适应证是A.溃疡穿孔在12h以内,不伴脓毒性休
膀胱高度膨胀且又极度衰弱的患者,首次放尿不应超过A.1500ml B.600m
小肠的生理功能是A.运化水谷 B.宣发肃降 C.运化水液 D.分清别浊
已知某企业20×1年营业收入为2000万元,平均流动比率为2,平均流动负债为25
房地产买卖的房款支付需要控制风险,当前最安全的钱款交割方式有( )。A.一次性
“三个和尚”的故事中,“一个和尚挑水喝,两个和尚抬水喝,三个和尚没水喝”主要揭示
紫苏、生姜都具有的功效是A.发汗解表 B.行气宽中 C.解鱼蟹毒 D.止呕
最新回复
(
0
)