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
考研
The gravitational pull of the Earth and the Moon is important to us as we attempt to conquer more and more of outer-space.Here’s
The gravitational pull of the Earth and the Moon is important to us as we attempt to conquer more and more of outer-space.Here’s
admin
2015-06-11
42
问题
The gravitational pull of the Earth and the 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 is a point somewhere along that line, nearer to the Moon than to the Earth, at which the gravitation 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 the 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 the 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 fired 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 velocity of escape.This speed is about 25,000 miles 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.
According to the passage,the most difficult task of firing a rocket is______.
选项
A、to get the rocket into the space
B、to calculate the rocket’s velocity of escape
C、to guide the rocket after it leaves the Earth’s surface
D、to identify the gravitational fields of the Earth and the Moon
答案
C
解析
本题的依据句是“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.”从中可知C项为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/CXQi777K
0
在职申硕(同等学力)英语
相关试题推荐
Withthepossibleexceptionofequalrights,perhapsthemostcontroversialissueacrosstheUnitedStatestodayisthedeathpe
AWrittenEnglishhasbecomemoreBimportantlyinCbusinessEnglish,Dwiththeinventionofthefaxandthecomputer.
Learningdisabilitiesareverycommon.Theyaffectperhaps10percentofallchildren.Fourtimesasmanyboysasgirlshavelea
Insteadofansweringthequestion,themanager______hisshouldersasifitwerenotimportant.
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?WhatdoesVosswanttostressinthelastparagraph?
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?WhichofthefollowingisNOTTRUEaccordingtowhatVoss
Themainpurposeofthispassageistodiscuss______AccordingtoOswald,amoreimportantfactorinbringingabouthappiness
PromptnessisimportantinAmericanbusiness,academic,andsocialsettings.The【C1】______ofpunctualityistaughttoyoungch
随机试题
A.原发性肺结核B.急性粟粒性肺结核C.浸润性肺结核D.慢性纤维空洞性肺结核E.结核性胸膜炎
堵水井选层时,对非均质性或井网不完善、平面矛盾较大的井如何处理?
在Excel2010中,仅把某单元格的批注复制到另外单元格中,方法是_____。
慢性根尖周炎的诊断主要依靠
以下各项费用中不属于企业管理费的有()。
在建筑物30m以上的金属门窗、栏杆等应用()与均压环连接。
儒家贤能政治从人性本善出发,试图以人格“修齐”的方式实现道德政治,但往往因人性的善变而_________________;而民主政治以人性本恶为立论前提,特别强调权力来源的正当性、权力行使过程的外部制约性,将法度、制度嵌于个人道德与合理的政治之间,这就使得
设AND、OR和NOT分别表示按位与、按位或和按位求反运算,且X=10011011, Y=01111010,Z=111O1000,则(NOT(X)ANDY)=(6),(YORNOT(Z))=(7)。
二进制数0111110转换成十六进制数是
A、Theydon’tsellshirtshere.B、Thewomanshouldwaittilltheclothesareonsale.C、Theclotheshereareveryexpensive.D、He
最新回复
(
0
)