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Meteor stream is composed of dust particles that have been 2

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Meteor stream is composed of dust particles that have been 2 [#permalink] New post 27 Mar 2014, 08:07
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A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit. Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' individual orbits are perturbed by planetary gravitational fields. A recent computer-modeling experiment tested this hypothesis by tracking the influence of planetary gravitation over a projected 5,000-year period on the positions of a group of hypothetical dust particles. In the model,
the particles were randomly distributed throughout a computer simulation of the orbit of an actual meteor stream, the Geminid. The researcher found, as expected, that the computer-model stream broadened with time. Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor
stream. Surprisingly, the computer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.

Whenever the Earth passes through a meteor stream, a meteor shower occurs. Moving at a little over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over a day to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled "pipe" and one as it exited. There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.

Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 shows just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual
Geminid stream is about 3,000 years old.


Q3: The author states that the research described in the first paragraph was undertaken in order to

(A) determine the age of an actual meteor stream
(B) Identify the various structural features of meteor streams
(C) explore the nature of a particularly interesting meteor stream
(D) test the hypothesis that meteor streams become broader as they age
(E) show that a computer model could help in explaining actual astronomical data

OA:
[Reveal] Spoiler:
D

Explanation:
[Reveal] Spoiler:
P1 middle -> Astronomers has hypothesized that a meteor stream should broaden with time..
-> experiment tested this hypothesis....


Q4: It can be inferred from the passage that which of the following would most probably be observed during the Earth’s passage through a meteor stream if the conventional theories mentioned in line 14 were

(A) Meteor activity would gradually increase to a single, intense peak, and then gradually decline.
(B) Meteor activity would be steady throughout the period of the meteor shower.
(C) Meteor activity would rise to a peak at the beginning and at the end of the meteor shower.
(D) Random bursts of very high meteor activity would be interspersed with periods of very little activity.
(E) In years in which the Earth passed through only the outer areas of a meteor stream, meteor activity would be absent.

OA:
[Reveal] Spoiler:
A

OE:
[Reveal] Spoiler:
increasingly dense towards the centre


Q5: According to the passage, why do the dust particles in a meteor stream eventually surround a comet’s orginla orbit?

(A) They are ejected by the comet at differing velocities.
(B) Their orbits are uncontrolled by planetary gravitational fields.
(C) They become part of the meteor stream at different times.
(D) Their velocity slows over time.
(E) Their ejection velocity is slower than that of the comet.

OA:
[Reveal] Spoiler:
A

OE:
[Reveal] Spoiler:
First sentence -> dust particles that have been ejected from a parent comet at a variety of velocities



Q6: The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in line 14 and the new computer-derived theory?

(A) Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the steam.
(B) The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower.
(C) Over time the distribution of dust in a meteor stream will usually become denser at the outside edges of the stream than at the center.
(D) Meteor showers caused by older by older meteor streams should be, on average, longer in duration than those caused by very young meteor streams.
(E) The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams.

OA:
[Reveal] Spoiler:
D

OE:
[Reveal] Spoiler:
Both theories contend that meteor streams broaden over time.
Earth will experience longer showers with older stream, which is wider, than
the one with younger stream, which is narrower.


Q7: It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?

(A) Most meteor streams it encounters are more than 2,000 years old.
(B) When passing through a meteor stream, it usually passes near to the stream’s center.
(C) It crosses the Geminid meteor stream once every year.
(D) It usually takes over a day to cross the actual Geminid meteor stream.
(E) It accounts of msot of the gravitaitonal perturbation affecting the Geminid meteor stream.

OA:
[Reveal] Spoiler:
C


Q8: Which of the following is an assumption underlying the last sentence of the passage?

(A) In each of the years between 1970 and 1979, the Earth took exactly 19 hours to cross the Geminid meteor stream.
(B) The comet associated with the Geminid meteor stream has totally disintegrated.
(C) The Geminid meteor stream should continue to exist for at least 5,000 years.
(D) The Geminid meteor stream has not broadended as rapidly as the conventiona ltheories would have predicted.
(E) The computer-model Geminid meteor stream provides an accurate representation of the development of the
actual Geminid stream.

OA:
[Reveal] Spoiler:
E

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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 29 Jan 2015, 05:57
Q7: It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?

(C) It crosses the Geminid meteor stream once every year.

I don't really understand. Where does it state anything about crossing a stream once every year?
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 31 Jan 2015, 23:20
Expert's post
Combine the first sentence of paragraph 3 with the first sentence of paragraph 2. P3 tells us there is an annual Geminid meteor shower. P2 tells us that meteor showers occur when we pass through a meteor stream. It's pretty common that even when they ask you to infer from one part of the passage, you have to use what you've learned elsewhere in the passage to interpret that information.

Hope that helps!
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Meteor stream is composed of dust particles that have been 2 [#permalink] New post 01 Feb 2015, 09:24
5/6 correct : Completed in 12 min. 30 sec

Question 4 : Why is C not correct?

Can any one pls explain a bit more.
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 01 Feb 2015, 10:30
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In Q4, C matches what would happen if we were working with the distribution seen in the computer model--"a thick-walled, hollow pipe." Passing through that, we'd get a burst of activity, then a break (while we're in the "hollow" part) and then another burst. However, this computer model was a surprising deviation from conventional theories, which held that the distribution would be increasingly dense toward the center. Travelling through that, we'd expect activity to increase until we hit the peak and then taper off again.
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 06 May 2015, 00:33
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elenaekenger wrote:
Q7: It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?

(C) It crosses the Geminid meteor stream once every year.

I don't really understand. Where does it state anything about crossing a stream once every year?

As Dmitry has correctly mentioned, the following line from the passage basically gives this information: Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower?

So, the presence of "yearly" is the most strong indicator that Earth crosses the Geminid meteor stream once every year.

Quite tricky though; had to really strain my eyes.
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Meteor stream is composed of dust particles that have been 2 [#permalink] New post 29 Jul 2015, 14:05
goodyear2013 wrote:
A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit. Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' individual orbits are perturbed by planetary gravitational fields. A recent computer-modeling experiment tested this hypothesis by tracking the influence of planetary gravitation over a projected 5,000-year period on the positions of a group of hypothetical dust particles. In the model, the particles were randomly distributed throughout a computer simulation of the orbit of an actual meteor stream, the Geminid. The researcher found, as expected, that the computer-model stream broadened with time. Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream. Surprisingly, the computer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.

Whenever the Earth passes through a meteor stream, a meteor shower occurs. Moving at a little over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over a day to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled "pipe" and one as it exited. There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.

Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 shows just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.

Q5: According to the passage, why do the dust particles in a meteor stream eventually surround a comet’s original orbit?

(A) They are ejected by the comet at differing velocities.
(B) Their orbits are uncontrolled by planetary gravitational fields.
(C) They become part of the meteor stream at different times.
(D) Their velocity slows over time.
(E) Their ejection velocity is slower than that of the comet.

OA:
[Reveal] Spoiler:
A

OE:
[Reveal] Spoiler:
First sentence -> dust particles that have been ejected from a parent comet at a variety of velocities



I was confused by this one. In the passage, it states that "A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities." I bolded the word parent because that implies the parent comet referenced and the comet the dust particles surround are two different comets. Thus, when the question asks about the comet that dust particles have surrounded, they are ejected by the "parent" comet, and not the comet that the dust particles surround. What am I missing? Why do they even bother to include the word "parent"? To trick out overthinkers like me?
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 29 Jul 2015, 21:48
Can anyone explain Q6? ... Where does it say that the conventional theory contends that meteor stream broadens over time?
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 29 Jul 2015, 22:12
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There are two references to this:

1) "Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' individual orbits are perturbed by planetary gravitational fields."

2) "The researcher found, as expected, that the computer-model stream broadened with time."

The first item is introducing an earlier idea ("conventional theory") that was validated by the computer model in the second item.

For a detailed analysis, check out our blog:

https://www.manhattanprep.com/gmat/blog ... m-passage/
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 03 Aug 2015, 06:48
can sum1 explain q6...i know that they hav mentioned yearly word..but v r questioning abt that n not answering..
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 11 Aug 2015, 13:12
DmitryFarber wrote:
There are two references to this:

1) "Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' individual orbits are perturbed by planetary gravitational fields."

2) "The researcher found, as expected, that the computer-model stream broadened with time."

The first item is introducing an earlier idea ("conventional theory") that was validated by the computer model in the second item.

For a detailed analysis, check out our blog:

https://www.manhattanprep.com/gmat/blog ... m-passage/


Hi Dmitry, Could you please explain question 8. I chose B , because if the comet existed then we may not have only 2 peak intervals but more and also the earth would be destroyed. In my opinion the last para does not state that the data used in 1970 to 1979 was from the model and not actually observed. Nor is it mentioned that to measure the time intervals we only use the computer model.

Please help me !!

Thanks and kudos !
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 14 Aug 2015, 21:20
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It's safe to say that if you are thinking about the possible destruction of the Earth, you have strayed too far from the text! ;) As in a CR assumption question, we want something that bridges the conclusion at hand with other information provided directly in the passage.

One way to test our answers is to apply the Negation Test. If we negate the text in a particular answer choice and that poses a problem for the argument, then we have found a necessary assumption. If it doesn't, then we can cross that answer out. Let's try. First we need to keep in mind what conclusion we're dealing with. The last line says that the stream is about 3,000 years old. Why does the author think so? Because of the time it takes to get from one burst of meteor activity to the other. How can we connect the distance between the edges and the age of the stream? With the earlier information about the development of the stream over time. The conventional theories say that the stream should get dense in the center, while the computer model predicts a shape more like the hollow pipe. The observations in the last paragraph seem to match the computer model, so the author figures that we can use that model to determine how long the stream took to get this way. Now let's look at how each answer choices relates once we negate:

(A) The Earth did not take exactly 19 hours to cross each year. This is fine. In fact, the passage makes it clear that the time should vary from year to year. 19 hours is just an average. Eliminate.

(B) The comet has not totally disintegrated. Well, what do we mean by totally disintegrated? There are still chunks? What are we supposed to do with that information. Maybe some meteors are bigger than others and maybe they aren't. This doesn't connect to anything we know about the size, shape, or age of the stream.

(C) The stream should not continue to exist for 5,000 years. Okay, but what we want to look at what has already happened. Also, the fact that the computer model covers a 5,000-year period does not tell us how much longer a 3,000-year-old meteor stream should last.

(D) The stream has broadened as rapidly as the conventional theory predicted. This might seem to support the conventional theory and thereby pose a threat to the author's view. However, the distinction the author is making in the last paragraph between the two theories is not how fast the stream broadens, but whether it condenses or hollows out in the center.

(E) The computer model does NOT provide an accurate representation of the development of the actual Geminid system. If that were the case, then it wouldn't be safe to use the model to determine the age of the system, even if its prediction about the hollow center seemed correct. If the stream took a much longer or shorter time to spread out than that predicted by the computer model, then it would not be safe to conclude that the stream is about 3,000 years old. Answer choice (E) as originally worded is a necessary assumption.

I hope that helps!
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Re: Meteor stream is composed of dust particles that have been 2 [#permalink] New post 15 Aug 2015, 04:56
DmitryFarber wrote:
It's safe to say that if you are thinking about the possible destruction of the Earth, you have strayed too far from the text! ;) As in a CR assumption question, we want something that bridges the conclusion at hand with other information provided directly in the passage.

One way to test our answers is to apply the Negation Test. If we negate the text in a particular answer choice and that poses a problem for the argument, then we have found a necessary assumption. If it doesn't, then we can cross that answer out. Let's try. First we need to keep in mind what conclusion we're dealing with. The last line says that the stream is about 3,000 years old. Why does the author think so? Because of the time it takes to get from one burst of meteor activity to the other. How can we connect the distance between the edges and the age of the stream? With the earlier information about the development of the stream over time. The conventional theories say that the stream should get dense in the center, while the computer model predicts a shape more like the hollow pipe. The observations in the last paragraph seem to match the computer model, so the author figures that we can use that model to determine how long the stream took to get this way. Now let's look at how each answer choices relates once we negate:

(A) The Earth did not take exactly 19 hours to cross each year. This is fine. In fact, the passage makes it clear that the time should vary from year to year. 19 hours is just an average. Eliminate.

(B) The comet has not totally disintegrated. Well, what do we mean by totally disintegrated? There are still chunks? What are we supposed to do with that information. Maybe some meteors are bigger than others and maybe they aren't. This doesn't connect to anything we know about the size, shape, or age of the stream.

(C) The stream should not continue to exist for 5,000 years. Okay, but what we want to look at what has already happened. Also, the fact that the computer model covers a 5,000-year period does not tell us how much longer a 3,000-year-old meteor stream should last.

(D) The stream has broadened as rapidly as the conventional theory predicted. This might seem to support the conventional theory and thereby pose a threat to the author's view. However, the distinction the author is making in the last paragraph between the two theories is not how fast the stream broadens, but whether it condenses or hollows out in the center.

(E) The computer model does NOT provide an accurate representation of the development of the actual Geminid system. If that were the case, then it wouldn't be safe to use the model to determine the age of the system, even if its prediction about the hollow center seemed correct. If the stream took a much longer or shorter time to spread out than that predicted by the computer model, then it would not be safe to conclude that the stream is about 3,000 years old. Answer choice (E) as originally worded is a necessary assumption.

I hope that helps!


Thank you so much for such a detailed analysis and explanation.
As you have pointed out Option B is not connecting the dots. In my mind Option E is the clear answer now.

Thanks again and kudos !!
Re: Meteor stream is composed of dust particles that have been 2   [#permalink] 15 Aug 2015, 04:56
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