2010年10-11月GMAT閱讀真題（至11.7）（二十六）
2.3.5 小行星撞擊 △★
V1【BY：手塚彌生】
最后一篇想起來(lái)叻 小行星撞碎 據(jù)說(shuō)是GWD?本人沒(méi)做到過(guò)。。還是做太少。。 以下是我百度到的。。就是這哥們說(shuō)的這個(gè)。。
V2【BY：米米喵】
(這位狗主人的描述是依據(jù)本篇的原文，見(jiàn)下面dumdumface搜索的英文)
LZ做到的只有后2段，一個(gè)問(wèn)文章的主要目的，一個(gè)問(wèn)文章的結(jié)構(gòu)，一個(gè)問(wèn)削弱最后一段的第一句里的evident的。還有一個(gè)，繞了一大圈，問(wèn)那些旋轉(zhuǎn)的速度快得足以讓行星fly apart的小行星一定是以下哪一種(囧，表達(dá)不能)。LZ的思路是這樣的：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?yàn)樾行莻兌疾荒苄D(zhuǎn)太快，否則他們會(huì)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，那些旋轉(zhuǎn)得那么快，又不會(huì)fly apart的，就是那些BUT FIVE，既那些exceptions了，所以選smaller than about 150 meters in diameter
應(yīng)該沒(méi)錯(cuò)吧，還是請(qǐng)N人確定一下。
V3【BY：wliu 690】
asternoids 的自傳速度。。。說(shuō)是轉(zhuǎn)的太快的就會(huì)造成自體分裂，除非是非常牢固的
V4【BY：cheeRse 760】11.7日
補(bǔ)充小行星撞擊第二段, 高亮escape velocity問(wèn)用處，請(qǐng)多讀兩遍機(jī)經(jīng)里的第二段，重點(diǎn)考
V5【BY：oliilo1986 770】11.7日
記得高亮了一大段“all exceptions are small stars with diameter smaller than 200”,問(wèn)什么不記得了，sorry….. 好像答它們都是monolithic
搜索 dumdumface (已確認(rèn))
...自己讀了一下,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 left? 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.
(考過(guò)的狗主人說(shuō)第二段重點(diǎn)考，請(qǐng)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.
V3【BY：victorss 780】
隕石撞擊：無(wú)非就是變快變慢有兩個(gè)條件：合成的/非合成 - 轉(zhuǎn)的快/慢 分清楚4種情況就沒(méi)問(wèn)題
V4【BY tyn0328 750】
狗狗上那個(gè)原文比較像，大家好好看看吧。這個(gè)題目出的很惡心，我有兩題都很像邏輯題。注意看懂那個(gè)速度和大小的關(guān)系。
V5【BY nyliangnan 730】
小行星撞擊，說(shuō)的是組成成分是R什么的撞擊后速度很集中，另外成分的撞擊后的有很快的也有很慢的。這個(gè)我沒(méi)大看懂，請(qǐng)大家補(bǔ)充~
2.3.5 小行星撞擊 △★
V1【BY：手塚彌生】
最后一篇想起來(lái)叻 小行星撞碎 據(jù)說(shuō)是GWD?本人沒(méi)做到過(guò)。。還是做太少。。 以下是我百度到的。。就是這哥們說(shuō)的這個(gè)。。
V2【BY：米米喵】
(這位狗主人的描述是依據(jù)本篇的原文，見(jiàn)下面dumdumface搜索的英文)
LZ做到的只有后2段，一個(gè)問(wèn)文章的主要目的，一個(gè)問(wèn)文章的結(jié)構(gòu)，一個(gè)問(wèn)削弱最后一段的第一句里的evident的。還有一個(gè)，繞了一大圈，問(wèn)那些旋轉(zhuǎn)的速度快得足以讓行星fly apart的小行星一定是以下哪一種(囧，表達(dá)不能)。LZ的思路是這樣的：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?yàn)樾行莻兌疾荒苄D(zhuǎn)太快，否則他們會(huì)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，那些旋轉(zhuǎn)得那么快，又不會(huì)fly apart的，就是那些BUT FIVE，既那些exceptions了，所以選smaller than about 150 meters in diameter
應(yīng)該沒(méi)錯(cuò)吧，還是請(qǐng)N人確定一下。
V3【BY：wliu 690】
asternoids 的自傳速度。。。說(shuō)是轉(zhuǎn)的太快的就會(huì)造成自體分裂，除非是非常牢固的
V4【BY：cheeRse 760】11.7日
補(bǔ)充小行星撞擊第二段, 高亮escape velocity問(wèn)用處，請(qǐng)多讀兩遍機(jī)經(jīng)里的第二段，重點(diǎn)考
V5【BY：oliilo1986 770】11.7日
記得高亮了一大段“all exceptions are small stars with diameter smaller than 200”,問(wèn)什么不記得了，sorry….. 好像答它們都是monolithic
搜索 dumdumface (已確認(rèn))
...自己讀了一下,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 left? 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.
(考過(guò)的狗主人說(shuō)第二段重點(diǎn)考，請(qǐng)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.
V3【BY：victorss 780】
隕石撞擊：無(wú)非就是變快變慢有兩個(gè)條件：合成的/非合成 - 轉(zhuǎn)的快/慢 分清楚4種情況就沒(méi)問(wèn)題
V4【BY tyn0328 750】
狗狗上那個(gè)原文比較像，大家好好看看吧。這個(gè)題目出的很惡心，我有兩題都很像邏輯題。注意看懂那個(gè)速度和大小的關(guān)系。
V5【BY nyliangnan 730】
小行星撞擊，說(shuō)的是組成成分是R什么的撞擊后速度很集中，另外成分的撞擊后的有很快的也有很慢的。這個(gè)我沒(méi)大看懂，請(qǐng)大家補(bǔ)充~