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
36
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:https://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
Ifyouareayoungcollegestudent,mostofyourconcernsaboutyourhealth
软木制品系栓树的外皮加工而成,是一种优异的保温隔热、防震、吸音材料,下面列举的软
全口义齿初戴时,下列哪项不是选磨的主要原因A.垂直距离一般均过高 B.架不可能
IFG的诊断标准是()A.≥7.8mmoI/L-<11.1mmol/L B.
扰动的黏质土在饱和状态下,因干燥收缩至体积不变的含水率称为()。A.液限 B
证券公司未按照规定对离任的法定代表人或者高级管理人员进行审计,并报送审计报告的,
2020年,全国集成电路出口单价约为多少元/个?A.5.2 B.4.3
遗传素质是人身心发展的( )。 A.主导因素 B.决定因素 C.物质前提
(2020年真题)企业发生的产品广告费记入的会计科目是()。A.主营业务成本
根据《生产安全事故报告和调查处理条例》,对事故发生单位主要负责人处上一年年收入4
最新回复
(
0
)