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
46
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
Whichofthefollowingnumbersisfarthestfromthenumber1onthenumberline?
Inaboxof10electricalparts,2aredefective.(a)Ifyouchooseonepartatrandomfromthebox,whatistheprobabilitythat
Fromasetof100numbers,halfwereselectedtoformgroupI,and60percentoftheremainingnumberswereselectedtoformgro
Thestandarddeviationofnnumbersx1,x2,x3,…,xnwithmeanisequalto,whereSisthesumofthesquareddifferences(x1
ListL:4,5,6,7,7,8,xListLconsistsof7numbers.Whichofthefollowingsetsconsistsofallvaluesofxforwhichthea
Thestandarddeviationofnnumbersx1,x2,x3…,xnwithmeanisequalto,whereSisthesumofthesquareddifferences(xi-)2
随机试题
下列政策属于政治政策的有()
在所有物质中,氢的原子最简单、最小,故氢的熔点、沸点也最低。()
阅读《种树郭橐驼传》中的一段文字,然后回答问题。……他植者则不然,根拳而土易,其培之也,若不过焉则不及。苟有能反是者,则又爱之太殷,忧之太勤,旦视而暮抚,已去而复顾,甚者爪其肤以验其生枯,摇其本以观其疏密,而木之性日以离矣。虽日爱之,其实害之
脐静脉插管后导管末端应位于( )。
某1万只雏鸡群,21日龄时发病,迅速传及全群。病鸡伸颈张口呼吸,喷嚏,流鼻汁,咳嗽。剖检发现气管、支气管和鼻腔内有浆液性、卡他性或干酪样分泌物,喉头和气管黏膜潮红、水肿,但无明显出血。常用于紧急接种的疫苗毒株是
征税对象又称为()。
位于市区的某制药公司由外商持股80%,且为增值税一般纳税人,该公司2020年向境外股东企业支付全年技术咨询指导费120万元,该公司当年应扣缴的增值税为()万元。
在下列所表示的不等式的解集中,不包括一5的是().
党的十八大报告指出,我国发展仍处于大有作为的()。
假设二叉树采用二叉链表存储结构存储,设计一个算法,求先序遍历序列中第k(1≤k≤二叉树中结点个数)个结点的值,要求:根据设计思想,采用C或C++语言描述算法,关键之处给出注释。
最新回复
(
0
)