OG When asteroids collide

[AbeNeedsAnswers]

When asteroids collide, some collisions cause
an asteroid to spin faster; others slow it down. If
asteroids are all monoliths-single rocks-undergoing
random collisions, a graph of their rotation rates
should show a bell-shaped distribution with statistical
"tails" of very fast and very slow rotators. If asteroids
are rubble piles, however, the tail representing the
very fast rotators would be missing, because any
loose aggregate spinning faster than once every few
hours (depending on the asteroid's bulk density)
would fly apart. Researchers have discovered that
all but five observed asteroids obey a strict limit on
rate of rotation. The exceptions are all smaller than
200 meters in diameter, with an abrupt cutoff for
asteroids larger than that.

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 after the collision those bits will usually move
slower than their mutual escape velocity. Over several
hours, gravity will reassemble all but the fastest
pieces into a rubble pile. 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.

537) The passage implies which of the following about the five asteroids mentioned in line 12?
A. Their rotation rates are approximately the same.
B. They have undergone approximately the same number of collisions.
C. They are monoliths.
D. They are composed of fragments that have escaped the gravity of larger asteroids.
E. They were detected only recently.

538) The discovery of which of the following would call into question the conclusion mentioned in line 16?
A. An asteroid 100 meters in diameter rotating at a rate of once per week
B. An asteroid 150 meters in diameter rotating at a rate of 20 times per hour
C. An asteroid 250 meters in diameter rotating at a rate of once per week
D. An asteroid 500 meters in diameter rotating at a rate of once per hour
E. An asteroid 1,000 meters in diameter rotating at a rate of once every 24 hours

539) According to the passage, which of the following is a prediction that is based on the strength of the gravitational attraction of small asteroids?
A. Small asteroids will be few in number.
B. Small asteroids will be monoliths.
C. Small asteroids will collide with other asteroids very rarely.
D. Most small asteroids will have very fast rotation rates.
E. Almost no small asteroids will have very slow rotation rates.

540) The author of the passage mentions "escape velocity" (see line 22) in order to help explain which of the following?
A. The tendency for asteroids to become smaller rather than larger over time
B. The speed with which impact fragments reassemble when they do not escape an asteroid's gravitational attraction after a collision
C. The frequency with which collisions among asteroids occur
D. The rotation rates of asteroids smaller than 200 meters in diameter
E. The tendency for large asteroids to persist after collisions

Q537: C
Q538: D
Q539: B
Q540: E

[pnwong]

Could anyone help with this passage? This one is pretty tough.... Thanks in advance!

[ravimschandra]

Key Points
Para 1
1. When asteroids collide, pieces may be slowed down or may be faster.
2. If it is single piece (monolith), their rotation rate is varying i.e.in bell shaped curve.
3. If they are more pieces (rubble pile), they follow consistent rate.
4. Sometimes, few faster pieces in rubble may fly apart from pile.
5. Only 5 asteroids not following - strict limit on rate of rotation.
6. They are smaller than 200 meters.
7. Smaller means faster.
Para 2
1. Asteroids larger than 200 meters are rubble piles.
2. The conclusion is evident that transition dia is 200 meters.
3. After collision, pieces move slower than velocity to move outside.
4. After some time, they gather together.it is because of gravity.
5. Collisions in asteroids are regular.
6. Small pieces in collision: as they are faster, they escape outside. most small asteroids should be monolithic

537) The passage implies which of the following about the five asteroids mentioned in line 12?
A. Their rotation rates are approximately the same.
It is indicated that they are not following strict rate of rotation. Nowhere it is mentioned that their rotation are rates are same. Hence it is wrong choice.
B. They have undergone approximately the same number of collisions.
Detail is out of scope from the passage
C. They are monoliths.
Author's Info - all but five five observed asteroids obey a strict limit on rate of rotation
Hence their rate of rotation is varying.
Remind Passage 1, Point 2 - If it is single piece (monolith), their rotation rate is varying i.e.in bell shaped curve.
Hence they are monoliths.
Right Answer is - C.

D. They are composed of fragments that have escaped the gravity of larger asteroids.
Author gave details regarding the rate of rotation. Author did not gave any other details regarding these 5 asteroids. Hence it is wrong choice

E. They were detected only recently.
The information is in present perfect. So we may attract to this answer. But they did not mention any indications that it is recent. So it is wrong answer.

538) The discovery of which of the following would call into question the conclusion mentioned in line 16?

What is Conclusion mentioned in line 16 ?
1. The evident conclusion agrees with recent computer modelling of collisions
2. asteroids larger than 200 meters across are multicomponent structures or rubble piles-

Next - What is recent computer modelling of collisions?
Smaller moves faster, bigger moves consistently.

Additional info regarding big stones - any loose aggregate spinning faster than once every few hours (depending on the asteroid's bulk density) would fly apart.

Based on above two info, we should understand that bigger ones rotates slower than few hours.

Question is - which of the following would call into question the conclusion?

It means we should identify which answer object the conclusion absolutely.
Hence we need to eliminate the asteroid bigger than 200 meters , and rotating faster than few hours.




A. An asteroid 100 meters in diameter rotating at a rate of once per week
Smaller than 200 meters . wrong answer
B. An asteroid 150 meters in diameter rotating at a rate of 20 times per hour
Smaller than 200 meters . wrong answer
C. An asteroid 250 meters in diameter rotating at a rate of once per week
Larger than 200 meters. But rotating slowly. Hence wrong answer
D. An asteroid 500 meters in diameter rotating at a rate of once per hour
Larger than 200 meters. But rotating at an hour. Hence it is right answer.- D
E. An asteroid 1,000 meters in diameter rotating at a rate of once every 24 hours
Larger than 200 meters. But rotating slowly. Hence wrong answer

539) According to the passage, which of the following is a prediction that is based on the strength of the gravitational attraction of small asteroids?


A. Small asteroids will be few in number.
Out of scope.
B. Small asteroids will be monoliths.
Refer the last 2 lines - most small asteroids should be monolithic, because impact fragments easily escape their feeble gravity.
It is clearly mentioned that due to their feeble gravity , they are monolithic.
This right answer. -D
C. Small asteroids will collide with other asteroids very rarely.
It is mentioned that asteroids collides regularly. They did not mention any connection in between the gravity and collision. Hence we need eliminate this. Wrong answer.
D. Most small asteroids will have very fast rotation rates.
This also may be true as per the passage. But they did not mention any connection in between the gravity and rotation rate. Hence we need eliminate this. Wrong answer.
E. Almost no small asteroids will have very slow rotation rates.
They did not mention any connection in between the gravity and rotation rate. Hence we need eliminate this. Wrong answer.

540) The author of the passage mentions "escape velocity" (see line 22) in order to help explain which of the following?

A. The tendency for asteroids to become smaller rather than larger over time
This answer gives general info of what happens after a collision. But it does not refer to escape velocity. Hence wrong answer.
B. The speed with which impact fragments reassemble when they do not escape an asteroid's gravitational attraction after a collision
This seems correct. But there is flaw. Escape velocity is speed of the asteroid above which bits may move outside. It is not the speed which impacts reassemble. Hence wrong answer.
C. The frequency with which collisions among asteroids occur
Out of scope. There is no discussions regarding frequency of collisions.
D. The rotation rates of asteroids smaller than 200 meters in diameter
There is no info regarding rotation rates in this context. Hence wrong answer.

E. The tendency for large asteroids to persist after collisions
If the bits moved FASTER than their mutual escape velocity, then the bits would "escape" from each other and the large asteroid would remain blown to bits.
However, if the bits move SLOWER than their mutual escape velocity, the bits will not escape from each other and, instead, will reassemble due to gravity. Thus, after being blown to bits, most of the bits of the large asteroid will reassemble, explaining the tendency for large asteroids to persist after collisions. (E) is the correct choice.