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
外语
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 wh
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 wh
admin
2012-06-18
72
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 the pull of 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 Earth is, in some ways, less of a problem. The Earth’s gravitational field reaches far closer to the moon man 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 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 Earth.
It can be seen that if a rocket misses its target, it keeps on traveling through space until_______.
选项
A、it burns up
B、it is caught in the gravitational field of another planet
C、it is brought back to the Earth by scientists
D、it runs out of fuel
答案
B
解析
本题的依据句是“A rocket fired at the moon and continuing in the direction in which it was firedwould miss the moon by a wide margin and perhaps continue to drift out into space until‘captured’in another planet’s gravitational field.”从中可知B项为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/28nO777K
0
考博英语
相关试题推荐
Theteacherofreadingisinvolved,whetherthisisconsciouslyrealizedornot,inthedevelopmentofaliteratesociety.Ande
Inadditiontoredistributingincomes,inflationmayaffectthetotalrealincomeandproductionofthecommunity.Anincreasei
Therearesome______betweentheirtwodescriptions;wearepuzzledwhichweshouldbelieve.
In116,anapparentlyinsignificanteventinaremotepartofNorthernEurope______Europeintoabloodywar.
我想重新回到生活简简单单的时代。那时你所知道的只有色彩、乘法表和童谣(nurseryrhymes),但是你不觉得缺什么——你不知道你所不了解的,所以也不会去在乎。你所知道的只是开心快乐,因为你对一切令人忧虑、沮丧的事物都浑然(blissfully)不觉。
Theteacher______fromhercustomandgaveusnohomeworkyesterday.
Thecomingofautomationis______tohaveimportantsocialconsequences.
Atthesametime,medicalandsocialscienceresearchbegantoindicatethatretirementitselfhaddetrimentaleffects.
毫无疑问,有些妇女坚持要有离婚的权利,如果她们的丈夫干的工作和积攒的钱不如她们多的话。
如同人员与货物一样,人的思想观念也可以跨跃大西洋自由地交流,尽管有时会略显迟缓。
随机试题
A.沙参麦冬汤B.益胃汤C.左归丸D.补肝汤E.补肺汤肝阴虚之虚劳治宜
乳房后脓肿切开术的切口位置应在
淤胆型肝炎的诊断下列哪项是错误的()
根据《建设工程施工劳务分包合同(示范文本)》(GF—2003—0214),应由劳务分包人承担的工作费用是()。
下列不属于注册会计师在财务报表审计中的具体审计计划所包括的内容的是()。
下图为某特大城市及其周边地区各类土地付租能力与该地区地形剖面示意图,读图回答下列问题。a、b、c城市功能分区分别可能是()。
8名男生和4名女生站成一排,4名女生都不相邻的排法共有__________种.
下列说法正确的有()。
甲死后留有房屋1套、存款3万元和古画1幅。甲生前立有遗嘱,将房屋分给儿子乙,存款分给女儿丙,古画赠予好友丁,并要求丁帮丙找份工作。下列哪种说法是正确的?()
世界上最早实行宪政的国家是()。
最新回复
(
0
)