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
65
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] The velocity of escape is about ______.
选项
A、40,200 miles per minute
B、25,000 kilometers per hour
C、40,200 kilometers per hour
D、25,000 miles per minute
答案
C
解析
细节理解题。本题答案可在最后一段找到。本题的迷惑之处在于单位的变换,一定要看清再做决定。
转载请注明原文地址:https://tihaiku.com/zcyy/2973849.html
相关试题推荐
[originaltext]Currentstudiesshowthatwhatgoesonlabelsisanimportant
[originaltext]Currentstudiesshowthatwhatgoesonlabelsisanimportant
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
Listeningtoothersisanevenmoreimportantpartofcommunicationthanspe
随机试题
Whatshouldthestudentsbringwiththemtotheexam?[br][originaltext]No
发展不平衡问题依然突出,缩小贫富差距、共享全球化成果任重道远。[br][audioFiles]2018m8x/audio_etrktsj_201807_0
[img]2018m9s/ct_etoefz_etoeflistz_201808_0005[/img][br]Accordingtothediscus
Ofallthingsintheworld,Imostdislikefillingupforms;infact,Ihave
[originaltext]M:Anyway,Jessica,Ithinkwhetheryouenjoyhavingfriendsorn
[originaltext]M:Didyoumindcomingbackbycoachinsteadofbytrain?W:No,
张先生,43岁,汉族中层干部,身高168Cm,体重75kg,血压144/89mm
读部分地理事物数量的纬度差异示意图,回答下题。 下列叙述,符合图中所示的动
站用直流电源系统精益化评价细则中要求直流回路严禁采用(),应采用(
关于非全日制用工,下列说法错误的是:A.双方可订立口头协议 B.双方可约定30
最新回复
(
0
)