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
2025-04-26
20
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 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 than does the moon’s to Earth. Thus it will be necessary to fire an Earth-bound 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. [br] A rocket might miss its target,by a "wide margin". This means the rocket missed the target____.
选项
A、because of mechanical failure
B、by a great deal
C、by a small distance
D、because the target moved
答案
B
解析
题目问:火箭可能会错过一个“有广泛回旋余地“的目标,这句话意味着什么?本题可用排除法。A项“由于机械故障”,C项“距离短”。D项“因为目标移动”都不是文中所提原因。因此只有B项为正确答案。
转载请注明原文地址:https://tihaiku.com/zcyy/4054282.html
相关试题推荐
Thefuture______ofthebaldeagleisstillanimportantAmericanecologicalco
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingt
ThegravitationalpulloftheEarthandmoonisimportanttousasweattemp
ThegravitationalpulloftheEarthandmoonisimportanttousasweattemp
随机试题
()水量()煮时要高温[br]()紧闭外盖(
Thepassageismeantto______.[br]"...peoplewhodiewondering,’Whatif?’"(
在砂砾石层中进行钻孔灌浆施工的特点不包括()。A.在砂砾石层中钻孔和灌浆的
立即开始使用降压药物治疗的是()A.高危、很高危患者 B.3级高血压患
发病的重要条件是A.正气不足 B.邪盛而正未衰 C.邪气亢盛 D.正气与邪
简述现代企业人力资源管理各个历史发展阶段的特点。
咨询的终极目标与具体目标的关系是()。单选A.从终极目标着眼,从具体目标着手
基础心理学是研究()。 (A)正常成人心理现象的心理学基础学科 (B
在工程网络计划执行过程中,如果某项工作的进度偏差超过其自由时差,则该工作( )。
线下工程施工前,现场CP0、CPⅠ、CPⅡ控制桩和线路水准基点桩的交接工作由(
最新回复
(
0
)