首页
登录
职称英语
The gravitational pull of the earth and moon is important to us as we attemp
The gravitational pull of the earth and moon is important to us as we attemp
游客
2023-08-31
62
管理
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. [br] It can be inferred that if a rocket misses its target, it keeps on traveling through space until ______.
选项
A、it reaches the "black hole"
B、it is caught in the gravitational field of another planet
C、it runs out of fuel
D、it explodes
答案
B
解析
细节理解题。答案可在第四段第三句里找到。
转载请注明原文地址:http://tihaiku.com/zcyy/2973846.html
相关试题推荐
Itisimportantthat___________(展览馆的工程能如期竣工).theprojectoftheexhibitionce
Aweathermapisanimportanttoolforgeographers.Asuccessionofthreeor
Aweathermapisanimportanttoolforgeographers.Asuccessionofthreeor
Aweathermapisanimportanttoolforgeographers.Asuccessionofthreeor
Hard______(他们虽然尽了力),theirfirstattemptatasolutionwasunsuccessful.as/th
[originaltext]Breakfastplaysanimportantpartinourdallylife,anditsu
[originaltext]Breakfastplaysanimportantpartinourdallylife,anditsu
[originaltext]Breakfastplaysanimportantpartinourdallylife,anditsu
[originaltext]Memory,Ithink,isalmostasimportantasair,waterorsuns
[originaltext]Memory,Ithink,isalmostasimportantasair,waterorsuns
随机试题
SomeSuggestionsforPessimists[A]Obesityandsmokingmayb
Bush’sMBATwenty-sixof42
Whenyou’redrivingonamotorway,youmustobeythesignstellingyoutogetin
22February2006Ms.R
共用题干 FreeStatinswithFastFoodcould
《变电验收管理规定第26分册辅助设施验收细则》:智能组件柜(汇控柜)状态监测IE
小王家距离单位1.2公里,每天步行上班。速度为每分钟100米,则他上班需要花(
商业银行在计算资本充足率时,()无须从核心一级资本中全额扣除。A.商誉 B.
以下对周礼的基本原则表述正确的是:()A.“亲亲”“君君” B.“亲亲”
空气分离的基本方法不包括()。A.深度冷冻法 B.燃烧法 C.吸附法
最新回复
(
0
)