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
54
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?
Inaboxof10electricalparts,2aredefective.(a)Ifyouchooseonepartatrandomfromthebox,whatistheprobabilitythat
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
在Windows中,打开“资源管理器”窗口后,要改变文件或文件夹的显示方式.应选用()。
某病人夜间排尿次数增加,尿浓缩和稀释功能试验结果为24小时尿量1200ml,夜尿量800ml,比重为1.015~1.010,内生肌酐清除率为18ml/min,该病人可能为()
加速折旧法与平均使用年限法相比,并非一定缩短使用寿命,只是前期折旧多提,后期折旧少提,体现了稳健原则。()
某股权投资基金的已投项目出现以下情况,此时股权投资基金应重点关注的风险是()。Ⅰ.公司的资产负债率由年初的30%增长为年末的70%Ⅱ.公司的当年营业收入较去年有所增长,但净利润由盈利转为亏损Ⅲ.公司的流动比率、速动比率都有所提高
《义务教育数学课程标准(2011年版)》有两类行为动词,其中一类是描述结果目标的行为动词,包括“了解”“理解”“掌握”“运用”,请以“平行四边形”概念为例,说明“理解”的基本含义。
(2009年第1题)阅读下面短文,回答下列问题:在奥运会开幕式上,刘欢和莎拉.布莱曼演唱的主题曲《我和你》,音调悠扬婉转,意韵绵长。这几天常常在大街小巷听到这首歌,渐渐也熟悉了这旋律。熟悉一首歌是重要的,越听越会觉得平和中自有真挚的感情流露。这首歌的歌词
人们已经认识到,除了人以外,一些高级生物不仅能适应环境,而且能改变环境以利于自己的生存。其实,这种特性普遍存在,例如,一些低级浮游生物会产生一种气体,这种气体在大气层中转化为硫酸盐颗粒,这些颗粒使水蒸气浓缩而形成云。事实上,海洋上空的云层的形成很大程度上依
给定关系模式R,其中U为关系R的属性集,F是U上的一组函数依赖,X、Y、Z、W是U上的属性组。下列结论正确的是__________。
Delphi具有良好的数据处理能力,它所提供的______,可将数据从一种数据库全部或部分迁移到另一种数据库中。
【H1】【H6】
最新回复
(
0
)