12月考的加油啊！

离子键

祝贺你哦~~

我明天考,我也超怕阅读...希望沾点你的好运气~~

~~

[此贴子已经被作者于2006-12-20 22:54:12编辑过]

tricia1254

Astronomers theorize that a black

       hole forms when a massive object

       shrinks catastrophically（灾难地） under its own

 gravity, leaving only a gravitational（重力的）

  (5)field so strong that nothing escapes it.

Astronomers must infer the existence

of black holes, which are invisible,

from their gravitational influence on

the visible bodies surrounding them.

 (10)For example, observations indicate

that gas clouds in galaxy M87 are

whirling（旋转） unusually fast about the gal-

axy’s center.  Most astronomers

believe that the large concentration

 (15)of mass at the galaxy’s center is a

black hole whose gravity is causing

the gas to whirl.  A few skeptics have

argued that the concentration of mass

necessary to explain the speed of the

 (20)whirling gas is not necessarily a black

        hole:  the concentration in M87 might

        be a cluster of a billion or so dim stars.

  The same hypothesis might have

been applied to the galaxy NGC 4258,

 (25)but the notion of such a cluster’s

existing in NGC 4258 was severely

undermined when astronomers mea-

sured the speed of a ring of dust and

gas rotating close to the galaxy’s

 (30)center.  From its speed, they calcu-

lated that the core’s density is more

than 40 times the density estimated

       for any other galaxy.  If the center of

NGC 4258 were a star cluster, the

 (35)stars would be so closely spaced

that collisions between individual

stars would have long ago torn the

cluster apart.

 

Q10:

The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

1. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.
2. The concentration of mass at the center of M87 is probably a large cluster of dim stars.
3. The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.
4. The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.

5. The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.

 

--------------------------------------------------------------------------------

Q11:

The passage asserts which of the following about the existence of black holes?

             

1. Astronomers first speculated about the existence of black holes when they observed gas whirling around the center of a particular galaxy.
2. Evidence used to argue for the existence of black holes is indirect, coming from their presumed effects on other astronomical bodies.

3. Recent observations of certain astronomical bodies have offered proof.
4. A considerable body of evidence suggests the existence of black holes, even though their behavior is not completely consistent with the laws of physics.
5. Many astronomers are skeptical about certain recent evidence that has been used to argue for the existence of black holes.

 

--------------------------------------------------------------------------------

Q12:

Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?

             

1. The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.
2. A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.
3. The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.
4. Only one other galaxy has been observed to contain gas clouds whirling about its center as they do about the core of M87.
5. The gravitational force of a cluster of a billion or so dim stars would be sufficient to cause a whirling ring of gas and dust to collect around the center of a galaxy.

答案是A  ???????

 黑洞那篇是不是这个，mm请把答案确认一下哈~~

mccoist

恭喜MM～～本月的高分挺多的，真替大家高兴。

uibewsj

谢谢mccoist~多亏你带头啊

[此贴子已经被作者于2007-1-24 11:39:58编辑过]

nnii

舒其mm太牛了！

进来沾沾喜气！！

waterer

恭喜好心的mm，好人好报！！呵呵

[此贴子已经被作者于2006-12-21 2:37:09编辑过]

fantasy06

恭喜！

paulfrank11

太牛了！！！！

lazyratcn

12为啥是B阿？

shygirl369

LZ, 这道题怎么算的，我算的怎么不一样呀？

1。去年生产heater的profit和cost之比是20%，今年这两者之比降到5%，另一条件是两年的cost相同。问今年和去年heater的售价之比。答案是87.5%
去年：p1/c=20%

今年：p2/c=5%

so: S2/S1=p2-c/p1-c =5%c-c/20%c-c=95/80

错在哪了，请指点！谢谢！