选课中心
7099人选课
GMAT公开讲座
0元
GRE公开讲座
0元
一对一体验课
99元
GMAT模考网站
10000人
GRE模考网站
GMAT课程
GRE课程
托福辅导课程
【定制】1v1
私人订制
资料下载
考前冲刺
扫码添加助教
免费领取
备考资料大礼包
扫码关注公众号
本文来自GMAT阅读题库(点击查看更多),为考生提供GMAT阅读题目练习及答案解析,希望对大家GMAT备考有所帮助。点击下载更多GMAT备考必备资料。更多精彩尽请关注新东方在线GMAT频道!
GMAT阅读题目内容
Originally, scientists predicted small asteroids to be hard and rocky, as any loose surface material (called regolith) generated by impacts was expected to escape their weak gravity. Aggregate small bodies were not thought to exist, because the slightest sustained relative motion would cause them to separate. But observations and computer modeling are proving otherwise. Most asteroids larger than a kilometer are now believed to be composites of smaller pieces. Those imaged at high-resolution show evidence for copious regolith despite the weak gravity. Most of them have one or more extraordinarily large craters, some of which are wider than the mean ra dius of the whole body. Such colossal impacts would not just gouge out a crater—they would break any monolithic body into pieces. In short, asteroids larger than a kilometer across may look like nuggets of hard rock but are more likely to be aggregate assemblages—or even piles of loose rubble so pervasively fragmented that no solid bedrock is left.
The rubble hypothesis, proposed decades ago by scientists, lacked evidence, until the planetologist Schumaker realized that the huge craters on the asteroid Mathilde and its very low density could only make sense together: a porous body such as a rubble pile can withstand a battering much better than an integral object. It will absorb and dissipate a large fraction of the energy of an impact; the far side might hardly feel a thing. At first, the rubble hypothesis may appear conceptually troublesome. The material strength of an asteroid is nearly zero, and the gravity is so low one is tempted to neglect that too. The truth is neither strength nor gravity can be ignored. Paltry though it may be, gravity binds a rubble pile together. And anybody who builds sandcastles knows that even loose debris can cohere. Oft-ignored details of motion begin to matter: sliding friction, chemical bonding, damping of kinetic energy, etc. We are just beginning to fathom the subtle interplay of these minuscule forces.
The size of an asteroid should determine which force dominates. One indication is the observed pattern of asteroidal rotation rates. Some collisions cause an asteroid to spin faster; others slow it down. If asteroids are monolithic rocks undergoing random collisions, a graph of their rotation rates should show a bell-shaped distribution with a statistical “tail” of very fast rotators. If nearly all asteroids are rubble piles, however, this tail would be missing, because any rubble pile spinning faster than once every two or three hours fly apart. Recently, several astronomers discovered that all but five observed asteroids obey a strict rotation limit. The exceptions are all smaller than about 150 meters in diameter, with an abrupt cutoff for asteroids larger than 200 meters. The evident conclusion—that asteroids larger than 200 meters across are rubble piles—agrees with recent computer modeling of collisions. A collision can blast a large asteroid to bits, but those bits will usually be moving slower than their mutual escape velocity (the lowest velocity that a body must have in order to escape the orbit of a planet). Over several hours, gravity will reassemble all but the fastest pieces into a rubble pile.
4、According to the rubble-pile hypothesis, an advantage conferred on an asteroid held together by weak forces is that it is
A.unlikely to fall apart over a long period of time
B.more amenable to computer modeling
C.less vulnerable to the effects of powerful impacts
D.not likely to collide with another object
E.more readily observed by astronomers
GMAT直播VIP小班 | GMAT直播精讲班 | GMAT录播课 |
(VIP小班/全科班+1对1) | (全科精讲/单项备考) | (全科班/单项班) |
72.5课时 ¥18800 | 61课时 ¥7796 | 134课时 ¥14680 |
资料下载
新东方GMAT佛脚词汇1.0版本
发布时间:2023-06-30添加新东方美研助教号
回复【资料】获取
新东方GMAT数学500题资料下载
发布时间:2023-05-26添加新东方美研助教号
回复【资料】获取
新东方GMAT800题资料下载
发布时间:2022-05-21添加新东方美研助教号
回复【资料】获取
1000句GMAT真实句子改错问题
发布时间:2022-04-17添加新东方美研助教号
回复【资料】获取
2024杨鹏阅读难句(GMAT+GRE)教程
发布时间:2022-04-17添加新东方美研助教号
回复【资料】获取
新东方GMAT数学500题(解析及答案)
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
新东方GMAT800题(逻辑+语法+阅读)
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
新东方GMAT佛脚词汇1.0版本
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
GMAT词汇/长难句/语法资料大全
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
GMAT语文考试圣经(Bible)电子版
发布时间:2019-11-27关注新东方在线美研订阅号
回复【GMAT】获取
GMAT推理圣经PDF电子版
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
GMAT考试OG五个版本题号对照表
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
GMAT Ultimate Grammar电子书籍PDF
发布时间:2019-11-27添加新东方美研助教号
回复【资料】获取
添加美研助教号,
回复【GMAT】获取备考必看资料包
推荐阅读
更多>>新东方在线GMAT频道为大家带来GMAT阅读复习的五大步骤,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 1:原来
新东方在线GMAT频道为大家带来GMAT阅读背景的培养,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 一、经济学
新东方在线GMAT频道为大家带来GMAT阅读复习效率不高怎么办,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 建
新东方在线GMAT频道为大家带来GMAT阅读提高速度的根本方法,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 1
新东方在线GMAT频道为大家带来GMAT阅读如何避免错误,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 要避免GMA
新东方在线GMAT频道为大家带来GMAT阅读技巧的提升,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! GMAT阅读推
新东方在线GMAT频道为大家带来GMAT阅读备考的注意事项,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! GMAT阅
新东方在线GMAT频道为大家带来GMAT阅读怎么提高自己的能力,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 建
新东方在线GMAT频道为大家带来GMAT阅读长句子的备考,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 1 首先
新东方在线GMAT频道为大家带来GMAT阅读水平怎么提高,希望对大家GMAT备考有所帮助。更多精彩尽请关注新东方在线GMAT频道! 下面就来
资料下载
更多>>添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
关注新东方在线美研订阅号
回复【GMAT】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
添加新东方美研助教号
回复【资料】获取
阅读排行榜
相关内容