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
35
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
AShouldJohnresignandHenryBsucceedhim,weCwouldhavehadaDmorevigorousleadership.
Withthepossibleexceptionofequalrights,perhapsthemostcontroversialissueacrosstheUnitedStatestodayisthedeathpe
Learningdisabilitiesareverycommon.Theyaffectperhaps10percentofallchildren.Fourtimesasmanyboysasgirlshavelea
Forthispart,youaretowriteacompositionof120to150wordsonWhichisMoreImportant,WealthorHealth?Inyourcomposit
WhatdoTimeWarnerandMatsushitahaveincommon?Theissueofmediaownershipisimportantbecause______.
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?HowmanyflightswillVosshavefinishedifhisFour-mont
Oneofthereasonswhyscienceisimportantforchildrenisthatmanyofthemwill______Thereisnodoubtthatchildrenlike
Themainpurposeofthispassageistodiscuss______AccordingtoOswald,amoreimportantfactorinbringingabouthappiness
随机试题
围生期包括胎儿期一部分和婴儿期一部分,国内普遍采用的定义是
蜘蛛痣的特征应除外
在经济评价指标中,以下()属于动态指标。
工资数据替换是将符合条件的人员的某个工资项目的数据,统一替换成某个数据。()
L公司是一家知名的粤菜餐厅,在全国有100多家门店。为了在行业中始终保持领先地位,公司在内部设立了研究所,紧跟市场需求变化,定期开发特色菜上市,赢得了消费者好评。根据上述描述,L公司采取的发展战略类型是()。
冬天上学,某学生既怕寒冷而不愿意起床,又怕因迟到而受到老师的批评,由此产生的冲突是()。
幼儿园老师设计了一个摸彩球游戏,在一个不透明的盒子里混放着红、黄两种颜色的小球,它们除了颜色不同,形状、大小均一致。已知随机摸取一个小球,摸到红球的概率为三分之一。如果从中先取出3红7黄共10个小球,再随机摸取一个小球,此时摸到红球的概率变为五分之二,那么
设有关键码序列(Q,G,M,Z,A,N,B,P,X,H,Y,S,T,L,K,E),采用堆排序法进行排序,经过初始建堆后关键码值A在序列中的序号是
关于字节I/O流,下列叙述不正确的是
Low-agedOverseasStudentsLow-agedoverseasstudyhasbecomeamajorconcernbythemediaandparentsofthestudents,and
最新回复
(
0
)