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2017年10-11月GMAT阅读机经(至11.7)(二十七).

刚刚更新 编辑: 浏览次数:173 移动端

2.3.5 小行星撞击 △★

V1BY:手塚弥生】

最后一篇想起来叻 小行星撞碎 据说是GWD?本人没做到过。。还是做太少。。 以下是我百度到的。。就是这哥们说的这个。。

V2BY:米米喵】

(这位狗主人的描述是依据本篇的原文,见下面dumdumface搜索的英文)

LZ做到的只有后2段,一个问文章的主要目的,一个问文章的结构,一个问削弱最后一段的第一句里的evident的。还有一个,绕了一大圈,问那些旋转的速度快得足以让行星fly apart的小行星一定是以下哪一种(囧,表达不能)。LZ的思路是这样的: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 (depending on its bulk density) would fly apart.因为行星们都不能旋转太快,否则他们会fly apart,又Alan Harris of the Jet Propulsion Laboratory in Pasadena, Calif., Petr Pravec of the Academy of Sciences of the Czech Republic in Prague and their colleagues have 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 about 200 meters.

所以,那些旋转得那么快,又不会fly apart的,就是那些BUT FIVE,既那些exceptions了,所以选smaller than about 150 meters in diameter

应该没错吧,还是请N人确定一下。

V3BYwliu 690

asternoids 的自传速度。。。说是转的太快的就会造成自体分裂,除非是非常牢固的

V4BYcheeRse 76011.7

补充小行星撞击第二段, 高亮escape velocity问用处请多读两遍机经里的第二段,重点考

V5BYoliilo1986 77011.7

记得高亮了一大段“all exceptions are small stars with diameter smaller than 200,问什么不记得了,sorry.. 好像答它们都是monolithic

搜索 dumdumface (已确认)

...自己读了一下,有3段ms是原文

Yet the rubble-pile hypothesis is conceptually troublesome. The material strength of an asteroid is nearly zero, and gravity is so low you are tempted to neglect that, too. What’s lt? The truth is that neither strength nor gravity can be ignored. Paltry though it may be, gravity binds a rubble pile together. And anyone who builds sand castles knows that even loose debris can cohere. Oft-ignored details of motion begin to matter: sliding friction, chemical bonding, damping of kinetic energy, electrostatic attraction and so on. (In fact, charged particles from the sun can cause dust at the surface to levitate.) We are just beginning to fathom the subtle interplay

of these minuscule forces.

(考过的狗主人说第二段重点考,请大家注意!)

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 (depending on its bulk density) would fly apart. Alan Harris of the Jet Propulsion Laboratory in Pasadena, Calif., Petr

Pravec of the Academy of Sciences of the Czech Republic in Prague and their colleagues have discovered that all but five observed asteroids obey a strict rotation limit [see illustration on page 48]. The exceptions are all smaller than about 150 meters in diameter, with an abrupt cutoff for asteroids larger than about 200 meters.

The evident conclusion—that asteroids larger than 200 meters across are multicomponent structures or rubble piles—agrees with recent computer

modeling of collisions, which also finds a transition at that diameter. A collision can blast a large asteroid to bits, but those bits will usually be moving slower than their mutual escape velocity (which, as a rule of thumb, is about one meter per second, per kilometer of radius). Over several hours, gravity will reassemble all but the fastest pieces into a rubble pile [see illustration above]. Because collisions among asteroids are relatively frequent, most large bodies have already

suffered this fate. Conversely, most small asteroids should be monolithic, because impact fragments easily escape their feeble gravity.

V3BYvictorss 780

陨石撞击:无非就是变快变慢有两个条件:合成的/非合成 - 转的快/ 分清楚4种情况就没问题

V4BY tyn0328 750

狗狗上那个原文比较像,大家好好看看吧。这个题目出的很恶心,我有两题都很像逻辑题。注意看懂那个速度和大小的关系。

V5BY nyliangnan 730

小行星撞击,说的是组成成分是R什么的撞击后速度很集中,另外成分的撞击后的有很快的也有很慢的。这个我没大看懂,请大家补充~

V6BY ritarong11.5

是寂静上文字的第二段的第二句话开始一直到结尾,一共两断

题目(不按顺序的)

1.写法主旨题

2.问对于那些会fly appart的行星下面哪个是对的 只记得两个选项 一个说他们小于200 一个说他们大于200

3.问下面那个可以weaken第二段第三个单词的conclusion(高亮的)

5个选项的格式都是这样的:发现了一个多少多少米的小行星的转速是多少多少

这个要把文章逻辑搞清楚再选就行了 文章逻辑是这样的

monolithic 钟型分布(无limit <200的(考试的文章中好像不是150,直接搞了个200

rubble pies limit 转速不能超过once every two or three hours >200

关键是红字的地方 然后选违背这个逻辑的就行了

V7BY winow11.5

题目:“还有一个,绕了一大圈,问那些旋转的速度快得足以让行星fly apart的小行星一定是以下哪一种”这个题我也遇到了,题目很绕口的,不确定问的是飞出去的还是没飞出去的。我选的smaller than 200.(有选项是more than 200)。

考古 BY:手塚弥生 (已确认)

V1

记得说小行星被撞,速度会改变, 一些变大,一些变小,(一段末有题1,2), 第二断是计算机模拟这样的实验,好像有3,4

1)考第一段的段末, 关于small star 的速度什么的, 记得把原文的all small star 取非得Almost no small star, 好像选E

2) 想不起来了, 55555..

3) 文中提到 E** velocity (好像是急剧下降得速度)是为了说明什么? 不好定位, 我好像选了一个比较抽象得选项, 为了说明行星得某种变化状态

4)"transition"指什么?原文是transition at the diameter, 看到diameter, 所以我选了C, Size

V2

另一个人的 这俩人都是200408 09月的原始啊啊啊啊。。为什么我遇到这么老的题。。

第二篇就是什么那篇小行星相撞,是蛮搞的,以下是我的理解:科学家发现asteriod在撞击后旋状速度会受到影响,研究表明通常monolithic的小行星被撞后呈现钟形分布--也就是说大部分都集中在速度中等的这一区域,少数过快或者过慢的。不过,当小行星不是monolithic,而是什么rubble(不是一整块而是很多碎片)的时候,这个转的很快的小尾巴会消失(就是前面提到的钟行分布图中的右半部分)。 科学家发现大部分小行星都遵守这样的定律,除了 $('.wzy_bot .cs2').show(); $(".wzy_bot .cst .cst_num").click(function () { $(this).siblings().toggle() $(this).toggleClass("dangq_num") $(this).parent().siblings().children(".cs1").hide() $(this).parent().siblings().children(".cst_num").removeClass("dangq_num") }) $('.wzy_bot .da_btn').click(function(){ $(this).parent('p').next('div').slideToggle(500); })

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