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
The gravitational pull of the earth and moon is important to us as we attempt to conquer more and more of outer space. Here’s wh
The gravitational pull of the earth and moon is important to us as we attempt to conquer more and more of outer space. Here’s wh
admin
2013-06-02
67
问题
The gravitational pull of the earth and moon is important to us as we attempt to conquer more and more of outer space. Here’s why.
As a rocket leaves the earth, the pull of the earth on it becomes less and less as the rocket roars out into space. If you imagine a line between the earth and the moon, there’s a point somewhere along that line, nearer to the moon than to the earth, at which the gravitational pull of both the earth and the moon on an object is just about equal. An object placed on the moon side of that point would be drawn to the moon. An object placed on the earth side of that point would be drawn to the earth. Therefore, a rocket need be sent only to this "point of no return" in order to get it to the moon. The moon’s gravity will pull it the rest of the way.
The return trip of the rocket to the earth is, in some ways, less of a problem. The earth’s gravitational field reaches far closer to the moon than does the moon’s to earth. Thus, it will be necessary to fire an earthbound rocket only a few thousand miles away from the moon to reach a point where the rocket will drift to earth under the earth’s gravitational pull.
The problem of rocket travel is not so much concerned with getting the rocket into space as it is with guiding the rocket after it leaves the earth’s surface. Remember that the moon is constantly circling the earth. A rocket fired at the moon and continuing in the direction in which it was fired would miss the moon by a wide: margin and. perhaps continue to drift out into space until "captured" in another planet’s gravitational field. To reach the moon, a rocket must be tired toward the point where the moon will be when the rocket has traveled the: required distance. This requires precise calculations of the speed and direction of the rocket and of the speed and direction of the moon.
For a rocket to arrive at a point where the moon’s gravity will pull it the rest of the way, it must reach a speed called the velocity of escape. This speed is about 25, 000 m/les (about 40,200 kilometers) per hour. At a speed less than this, a rocket will merely circle the earth in an orbit and eventually fall back to the earth.
What does "an earthbound rocket" in Sentence 3 Para. 3 mean?
选项
A、A rocket sent from the earth to the moon.
B、A rocket sent from the moon to the earth.
C、A rocket made of earth.
D、A rocket with no purpose.
答案
B
解析
词汇理解题。本题也是对课文意思的间接考查,根据该句后面的阐述,我们知道这种火箭飞船是由月球向地球发射的,这样只要发射几千英里就可到达地、月之间的平衡点了。
转载请注明原文地址:https://kaotiyun.com/show/Q7B7777K
0
大学英语六级
相关试题推荐
Insciencethemeaningoftheword"explain"suffers【C1】______civilization’severystepinsearchofreality.Sciencecannotre
IsCollegeReallyWorththeMoney?TheRealWorldEsteGriffithhaditallfiguredout.WhenshegraduatedfromtheUn
A、Itcouldn’tgiveoutlightbyitself.B、ItistheonlysatellitetoGliese581.C、OnesideofOliese58lgconstantlyfacesGl
A、In1832.B、In1833.C、In1812.D、In1823.D选项表明,本题考查时间,听音时应留意与时间有关的信息,做好笔记。由男士提到TheErieCanal,whichwascompletedin1823可知,
Growingup,Iearnedmybestmarksforplayingwellwithothers.Formyhusband,Ilivedinthreedifferentcountriesinfiveye
A、Foreignproductsandexperts.B、TheinterestofyoungJapanese.C、Best-sellingJapanesetextbooks.D、Themediaandgovernment
7HealthProblemsfortheModernAgeModernlife,withitsemphasisoninformation,automation,computerization,andglobaliz
Pakistan’searthquakekilledmorethan70,000peopleandleftanother3.5millionhomeless.Almost10,000schoolsweredamagedo
A、Hewondersabouttheusefulnessoftheprotest.B、Hethinksthepresenttuitionisfair.C、Hedoesn’tknowhowmanystudentsp
A、Thereisanofficefurnitureshow.B、Thereisapaintingexhibition.C、Thereisamodernartcontest.D、Thereisanoff-season
随机试题
图示电路中,u=10sin(1000t+30°)V,如果使用相量法求解图示电路中的电流i,那么,如下步骤中存在错误的是:步骤1:;步骤2:=10.j1000C;步骤3:=I∠ψi;步骤4:。
建设单位应在工程竣工验收前()个工作日将验收时问、地点、验收组名单通知该工程的工程质量监督机构。
下列合同中,债权人不得将合同的权利全部或部分转让给第三人的有()。
某设备在5年的使用期中,年资产消耗成本分别为850元、400元、260元、200元、160元。年运行成本分别为200元、250元、300元、350元、400元,则这台设备的经济寿命为()年。
甲将一张汇票背书转让给乙,并在汇票上记载有“不得转让”字样,下列表述中正确的是()。
油脂类食物主要提供()。
坚持党对公安工作的()是我国公安工作的根本原则。
A.肝B.皮肤C.棕色脂肪组织D.骨骼肌人体最主要的散热器官是
Collegegraduatesarenowleavingschoolwithnotonlyadiploma,butalsowithmoredebtthaninanyotherperiodinhistory.A
Chinesestudentsare【21】willingtostudyveryhardforlonghours.Thisisanexcellent【22】,butitisoftenaninefficientmeth
最新回复
(
0
)