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【单选题】

Amphibious vehicles, those that can move on both land and water, have been in use for a number of years, but while most of them were fairly fast on land, they moved quite slowly when they were functioning as boats. The only truly amphibious vehicle that can move with equal ease on both land and water is the hovercraft (气垫船). The hovercraft is the invention of an electronics engineer named Christopher Cockerell. Cockerell’s hobby was sailing and he was interested in the problem of reducing the friction of water on the body of a boat, and hit on the idea of designing a boat which would travel on a cushion of air.
The air cushion under a hovercraft is produced by a large fan which blows air downwards between the craft and the water or ground, and so lifts up the craft. The air is main-rained at higher than atmospheric pressure by a flexible rubber "skirt" around the bottom edge of the hovercraft, pring leakage of air from the cushion. Because the hovercraft floats on the air cushion with no contact between the craft and the suce below, it can travel over flat, rough ground or water with ease.
Hovercraft are usually driven by air screws like propellers (螺旋桨), which face back-wards and "push" the craft forwards, and can be turned to direct the hovercraft. Since there is no propeller dipping below the craft, hovercraft can travel up slopes out of the water, or land on beaches.
Cockerell’s Air Cushion Vehicles, or ACVs, are now familiar to everyone and like all inventions, they have been improved upon. British Sea speed hovercraft have been carrying passengers and cars across the English Channel since 1968. They now have a "stretched" version of their Mountbatten Class hovercraft which can carry up to 60 cars and 416 passengers between Britain and France in a little over half an hour.
A new, large-sized hovercraft, designed and built in France, called the Sedam N500 of Naviplane, has now goneinto service. The 155 tonne N500 is 50 metres long (162 feet) and 23 metres wide (76 feet) and can carry 65 cars, plus five coaches, together with 400 passengers. When the sea conditions are ideal the N500 can reach 112 kph (70 mph).
A variation of the hovercraft principle is the sidewall ACV, which is more economical than the flexible skirt models, and easier to control, but it cannot be used on land. The United States Navy have been experimenting with warships based on the sidewall principle, and some of these may well reach a speed of 160kph (100mph).
According to the passage, Cockerell ______.

A.
usually spent his spare time in sailing
B.
was the first person who had the idea of designing amphibious vehicles
C.
liked to sail by ACVs
D.
is familiar with all the ACVs that have been ever produced
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参考答案:
举一反三

【单选题】螺旋桨的效率是_____

A.
指示功率与有效功率之比值
B.
螺旋桨的有效功率与消耗功率之比
C.
消耗功率与发出的功率之比
D.
指示功率与桨吸收功率之比

【单选题】165使用螺旋桨技术最主要的目的是

A.
降低人体射频能量的积累
B.
保证了图像的时间分辨力
C.
减少运动伪影
D.
减少带状伪影
E.
降低SNR

【单选题】螺旋桨桨叶扭转的目的是()。

A.
使从桨根到桨叶尖各剖面的的桨叶迎角基本相同
B.
使从桨根到桨叶尖的拉力大小基本相同
C.
使从桨根到桨叶尖的桨叶角大小基本相同

【单选题】螺旋桨推力功率THP为()。

A.
船舶主机发出的功率与传递效率的乘积
B.
螺旋桨发出的推力与螺旋桨进速(对水)的乘积
C.
螺旋業发出的推力与船速(对水)的乘积
D.
船舶阻力与船速的乘积
相关题目:
【单选题】螺旋桨的效率是_____
A.
指示功率与有效功率之比值
B.
螺旋桨的有效功率与消耗功率之比
C.
消耗功率与发出的功率之比
D.
指示功率与桨吸收功率之比
【单选题】165使用螺旋桨技术最主要的目的是
A.
降低人体射频能量的积累
B.
保证了图像的时间分辨力
C.
减少运动伪影
D.
减少带状伪影
E.
降低SNR
【单选题】螺旋桨桨叶扭转的目的是()。
A.
使从桨根到桨叶尖各剖面的的桨叶迎角基本相同
B.
使从桨根到桨叶尖的拉力大小基本相同
C.
使从桨根到桨叶尖的桨叶角大小基本相同
【单选题】螺旋桨推力功率THP为()。
A.
船舶主机发出的功率与传递效率的乘积
B.
螺旋桨发出的推力与螺旋桨进速(对水)的乘积
C.
螺旋業发出的推力与船速(对水)的乘积
D.
船舶阻力与船速的乘积
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