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
57
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
[originaltext]Ouronlinecoursesareopentothepublicforimmediatelyenrolme
【教学过程】 活动一:设置游戏,导入新课 游戏导入,教师分别展示钥匙,硬币,树叶等实物图和拓印图,让学生做找朋友的游戏,把相同的物品连接在一起,学生积极参与
根据大量调查,已知正常成年男子的心率μ=72次/分,σ=5次/分,从该总体中随机
与鼻咽癌的发生关系较为密切的是A.HSVB.CMVC.EBVD.VZVE.流感病
蓄电池组内阻测试要求,蓄电池内阻无明显异常变化,蓄电池组内阻偏离值应不大于出厂值
关于控制图控制限的说法,正确的有()。 A.分析用控制图的控制限与图上样本点的
战略性衡量项目主要有()。A.团队建设 B.队伍建设 C.制度建设 D.企
人在每一瞬间,将心理活动选择了某些对象而忽略了另一些对象。这一特点指的是注意的(
张某与郭某处于婚姻关系的正常存续期间中,二人经常因琐事而激烈争执,有天二人又开始
某双代号网络计划如下图所示(单位:天),则工作E的自由时差为()天。 A
最新回复
(
0
)