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
2025-05-11
24
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 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 to be sent only to this "point of no return" in order to get it to the moon. The moon’s gravity will pull it to 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 the 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 the Earth. [br] According to the passage, the most difficult task of firing a rocket is______.
选项
A、to get the rocket into the space
B、to calculate the rocket’s velocity of escape
C、to guide the rocket after it leaves the Earth’s surface
D、to identify the gravitational fields of the Earth and the moon
答案
C
解析
本题可参照“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.”,从中可知C项为正确答案。
转载请注明原文地址:http://tihaiku.com/zcyy/4071689.html
相关试题推荐
CommercialBanksCommercialbanksplayanimportantro
CommercialBanksCommercialbanksplayanimportantro
CommercialBanksCommercialbanksplayanimportantro
CommercialBanksCommercialbanksplayanimportantro
CommercialBanksCommercialbanksplayanimportantro
CommercialBanksCommercialbanksplayanimportantro
AllthemanagersarerequestedtoattendanimportantmeetingattheBoardMeeti
AllthemanagersarerequestedtoattendanimportantmeetingattheBoardMeeti
FiveInterviewingFundamentalsThemostimportantthing
FiveInterviewingFundamentalsThemostimportantthing
随机试题
第一回进山东,春正发生,出潼关沿着黄河古道走,同车里坐着几个和尚——和尚使我们与古代亲近——恍惚里,春秋战国的风云依然演义,我这是去了鲁国之境了。鲁国的土
[originaltext]Mensaidtheyspent13hoursaweekonhouseholddutyincludi
下列药材除哪个外均为果实A.地肤子B.五味子C.芥子D.川楝子E.使君子
分布式母线保护由主单元和若干个子单元组成,主单元实现保护功能,子单元执行跳闸功能
D解题指导:在图(1)的相同位置将直线变为曲线,曲线变为直线,得到图(2),依此规律将图(3)变化得到D。故答案为D。
为信息披露义务人履行信息披露义务出具专项文件的保荐机构、证券服务机构及其人员,违
(2019年真题)某男,42岁。5年前诊断为糖尿病,经中西药治疗,病情得以控制。
工程规模大、专业复杂的工程,建设单位管理能力有限时,选择施工队伍时应考虑采用()
凯恩斯货币需求理论的突出贡献是( )。A.消费性货币需求的分析 B.货币总需
2019年6月1日,黄河公司对某管理用固定资产进行更新改造。截止2019年10月
最新回复
(
0
)