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
Choose the most suitable headings for paragraphs B-Efrom the list of headings below. Write the appropriate numbers i-ix in boxes
Choose the most suitable headings for paragraphs B-Efrom the list of headings below. Write the appropriate numbers i-ix in boxes
admin
2014-05-25
47
问题
Choose the most suitable headings for paragraphs B-Efrom the list of headings below.
Write the appropriate numbers i-ix in boxes 1-4 on your answer sheet.
List of Headings
i How the reaction principle works
ii The impact of the reaction principle
iii Writers’ theories of the reaction principle
iv Undeveloped for centuries
v The first rockets
vi The first use of steam
vii Rockets for military use
viii Developments of fire
ix What’s next?
THE ROCKET - FROM EAST TO WEST
A The concept of the rocket, or rather the mechanism behind the idea of propelling an object into the air, has been around for well over two thousand years. However, it wasn’t until the discovery of the reaction principle, which was the key to space travel and so represents one of the great milestones in the history of scientific thought, that rocket technology was able to develop. Not only did it solve a problem that had intrigued man for ages, but, more importantly, it literally opened the door to exploration of the universe.
B An intellectual breakthrough, brilliant though it may be, does not automatically ensure that the transition is made from theory to practice. Despite the fact that rockets had been used sporadically for several hundred years, they remained a relatively minor artefact of civilisation until the twentieth century. Prodigious efforts, accelerated during two world wars, were required before the technology of primitive rocketry could be translated into the reality of sophisticated astronauts. It is strange that the rocket was generally ignored by writers of fiction to transport their heroes to mysterious realms beyond the Earth, even though it had been commonly used in fireworks displays in China since the thirteenth century. The reason is that nobody associated the reaction principle with the idea of travelling through space to a neighbouring world.
C A simple analogy can help us to understand how a rocket operates. It is much like a machine gun mounted on the rear of a boat. In reaction to the backward discharge of bullets, the gun, and hence the boat, move forwards. A rocket motor’s ’bullets’ are minute, high-speed particles produced by burning propellants in a suitable chamber. The reaction to the ejection of these small particles causes the rocket to move forwards. There is evidence that the reaction principle was applied practically well before the rocket was invented. In his Noctes Atticae or Greek Nights, Aulus Gellius describes ’the pigeon of Archytas’, an invention dating back to about 360 BC. Cylindrical in shape, made of wood, and hanging from string, it was moved to and fro by steam blowing out from small exhaust ports at either end. The reaction to the discharging steam provided the bird with motive power.
D The invention of rockets is linked inextricably with the invention of ’black powder’. Most historians of technology credit the Chinese with its discovery. They base their belief on studies of Chinese writings or on the notebooks of early Europeans who settled in or made long visits to China to study its history and civilisation. It is probable that, some time in the tenth century, black powder was first compounded from its basic ingredients of saltpetre, charcoal and sulphur. But this does not mean that it was Immediately used to propel rockets. By the thirteenth century, powder-propelled fire arrows had become rather common. The Chinese relied on this type of technological development to produce incendiary projectiles of many sorts, explosive grenades and possibly cannons to repel their enemies. One such weapon was the ’basket of fire’ or, as directly translated from Chinese, the ’arrows like flying leopards’. The 0.7 metre-long arrows, each with a long tube of gunpowder attached near the point of each arrow, could be fired from a long, octagonal-shaped basket at the same time and had a range of 400 paces. Another weapon was the ’arrow as a flying sabre’, which could be fired from crossbows. The rocket, placed in a similar position to other rocket-propelled arrows, was designed to increase the range. A small iron weight was attached to the 1.5m bamboo shaft, just below the feathers, to increase the arrow’s stability by moving the centre of gravity to a position below the rocket. At a similar time, the Arabs had developed the ’egg which moves and burns’. This ’egg’ was apparently full of gunpowder and stabilised by a 1.5m tail. It was fired using two rockets attached to either side of this tail.
E It was not until the eighteenth century that Europe became seriously interested in the possibilities of using the rocket itself as a weapon of war and not just to propel other weapons. Prior to this, rockets were used only in pyrotechnic displays. The incentive for the more aggressive use of rockets came not from within the European continent but from far-away India, whose leaders had built up a corps of rocketeers and used rockets successfully against the British in the late eighteenth century. The Indian rockets used against the British were described by a British Captain serving in India as ’an iron envelope about 200 millimetres long and 40 millimetres in diameter with sharp points at the top and a 3m-long bamboo guiding stick’. In the early nineteenth century the British began to experiment with incendiary barrage rockets. The British rocket differed from the Indian version in that it was completely encased in a stout, iron cylinder, terminating in a conical head, measuring one metre in diameter and having a stick almost five metres long and constructed in such a way that it could be firmly attached to the body of the rocket. The Americans developed a rocket, complete with its own launcher, to use against the Mexicans in the mid-nineteenth century. A long cylindrical tube was propped up by two sticks and fastened to the top of the launcher, thereby allowing the rockets to be inserted and lit from the other end. However, the results were sometimes not that impressive as the behaviour of the rockets in flight was less than predictable.
F Since then, there have been huge developments in rocket technology, often with devastating results in the forum of war. Nevertheless, the modern day space programs owe their success to the humble beginnings of those in previous centuries who developed the foundations of the reaction principle. Who knows what it will be like in the future?
Paragraph C
选项
答案
i // How the reaction principle works
解析
转载请注明原文地址:https://kaotiyun.com/show/jFNO777K
本试题收录于:
雅思阅读题库雅思(IELTS)分类
0
雅思阅读
雅思(IELTS)
相关试题推荐
Thefunction/hasthepropertythatf(x)=f(x+1)forallnumbersx.Iff(4)=17,whatisthevalueoff(8)?
Whichofthefollowingnumbersisfarthestfromthenumber1onthenumberline?
Fromasetof100numbers,halfwereselectedtoformgroupI,and60percentoftheremainingnumberswereselectedtoformgro
Thefunctionfhasthepropertythatf(x)=f(x+1)forallnumbersx.Andg(x)=f(x)+1.Whichofthefollowingstatementsmust
Theleastandgreatestnumberinalistof7realnumbersare2and20,respectively.Themedianofthelistis6,andthenumbe
Thestandarddeviationofnnumbersx1,x2,x3,…,xnwithmeanisequalto,whereSisthesumofthesquareddifferences(x1
Thesumofnnumbersisgreaterthan48.Iftheaverage(arithmeticmean)ofthennumbersis1.2,whatistheleastpossibleva
随机试题
关于子宫内膜异位症的治疗,下列说法正确的是()
A.霍乱弧菌B.空肠弯曲菌C.海鸥弯曲菌D.幽门螺杆菌E.副溶血弧菌25℃醋酸吲哚水解试验阳性
女性患者,23岁。间歇性心悸,气促3年,劳累时加重。1周前受凉后出现发热、咽痛、咳嗽,4天前出现心悸和气促加剧,双下肢水肿。查:T37℃,R34次/分,P108次/分,律不整,BP80/50mmHg。半坐位,四肢指(趾)端及唇轻度发绀,扁桃体Ⅱ肿大,无脓性
小青龙汤中主要起温肺化饮作用的药物是()
患者,女,18岁。每次月经错后10天左右,月经量少色淡,身倦乏力,头晕心悸,舌质淡,脉细弱。宜首选的药物类别是
患者,女性,65岁,严重腹泻、脱水,意识障碍。查体:血糖33,3mmol/L,尿酮体(±)。意识障碍发生的原因是
设备监理工程师在设备安装阶段协助业主的工作主要有( )。
口腔颌面外科常采用的闭式引流是()。
为类MyClass重载赋值运算符时,应将其重载为类的
Thestudyoftherelationshipbetweenlanguageandsocietyiscalled
最新回复
(
0
)