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manasveek
Rocket engines are most effective when exhaust gases escape from their nozzles at the same pressure as the surrounding atmosphere. At low altitudes, where atmospheric pressure is high, this effect is best produced by a short nozzle, but when the rocket passes through the thin upper atmosphere, a long nozzle becomes more effective. Thus, to work most effectively throughout their ascents, all rockets must have both short nozzles and long nozzles on their engines.

Which one of the following is an assumption the argument requires?

A) Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them with nozzles of equal lengths.

B) At some point during their ascents, all rockets will pass through the thin upper atmosphere.

C) A rocket with only short nozzles on its engines cannot reach high altitudes.

D) For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding atmosphere throughout the rocket's ascent.

E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.

Source: LSAT

Hi nightblade354 ,

Can you please explain how answer can be B
Even if the rocket does not pass through thin upper atmosphere it can still work effectively
because it might have either short or long nozzle which will still produce the best result. All in all I don't feel that B can break the conclusion.
Please explain how to arrive at this assumption.

Thanks in Advance
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manasveek
Rocket engines are most effective when exhaust gases escape from their nozzles at the same pressure as the surrounding atmosphere. At low altitudes, where atmospheric pressure is high, this effect is best produced by a short nozzle, but when the rocket passes through the thin upper atmosphere, a long nozzle becomes more effective. Thus, to work most effectively throughout their ascents, all rockets must have both short nozzles and long nozzles on their engines.

Which one of the following is an assumption the argument requires?

A) Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them with nozzles of equal lengths.

B) At some point during their ascents, all rockets will pass through the thin upper atmosphere.

C) A rocket with only short nozzles on its engines cannot reach high altitudes.

D) For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding atmosphere throughout the rocket's ascent.

E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.

Source: LSAT

Hi nightblade354 ,

Can you please explain how answer can be B
Even if the rocket does not pass through thin upper atmosphere it can still work effectively
because it might have either short or long nozzle which will still produce the best result. All in all I don't feel that B can break the conclusion.
Please explain how to arrive at this assumption.

Thanks in Advance

Hi,
The conclusion says..
Quote:
Thus, to work most effectively throughout their ascents, all rockets MUST have both short nozzles and long nozzles on their engines.
The catch is MUST. If it is NOT passing through the thin atmosphere, WHY does it require the LONG nuzzle. It should work effectively just with the short nuzzle because that is what the argument says.
But, the conclusion says that long nuzzle and short nuzzle are a MUST for working effectively. Thus, the rocket must be passing through the thin atmosphere.
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After reading the argument, I just thought how argument is written.
A simple requirement of short and long nozzle on rocket is mentioned.
Then it is concluded that all rocket must have both kinds of nozzle for their accents.

The first thought came into my mind- why both kinds of nozzles mandatory!
Do all rockets pass through upper thin layer? If no, Rockets don't need long nozzles.

B matched with my pre-thinking.

All other options are not convincing.
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If you could shed a bit of light on why E wouldnt be the answer
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chetan2u
manasveek
Rocket engines are most effective when exhaust gases escape from their nozzles at the same pressure as the surrounding atmosphere. At low altitudes, where atmospheric pressure is high, this effect is best produced by a short nozzle, but when the rocket passes through the thin upper atmosphere, a long nozzle becomes more effective. Thus, to work most effectively throughout their ascents, all rockets must have both short nozzles and long nozzles on their engines.

The short nozzle is for the atmosphere on Earth and the long nozzle for the thin upper atmosphere. All the rockets to be fitted with both of them means there is a requirement of both nozzles and that would occur only when the rocket has to cross the upper atmosphere too.- clearly this is the Assumption too

Which one of the following is an assumption the argument requires?

A) Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them with nozzles of equal lengths.
we require nozzles of both types and difficulty is not being talked of.

B) At some point during their ascents, all rockets will pass through the thin upper atmosphere.
Correct


C) A rocket with only short nozzles on its engines cannot reach high altitudes.
More efficient is the word and not that the short nozzle cannot cross upper atmosphere

D) For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding atmosphere throughout the rocket's ascent.
This is already given in para

E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.
again cannot be an assumption

B


I understand why B is correct and chose but the problem took me a bit of time because I wasnt able to conclusively eliminate OPTION E. Could you elaborate why E is wrong?
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chetan2u
manasveek
Rocket engines are most effective when exhaust gases escape from their nozzles at the same pressure as the surrounding atmosphere. At low altitudes, where atmospheric pressure is high, this effect is best produced by a short nozzle, but when the rocket passes through the thin upper atmosphere, a long nozzle becomes more effective. Thus, to work most effectively throughout their ascents, all rockets must have both short nozzles and long nozzles on their engines.

The short nozzle is for the atmosphere on Earth and the long nozzle for the thin upper atmosphere. All the rockets to be fitted with both of them means there is a requirement of both nozzles and that would occur only when the rocket has to cross the upper atmosphere too.- clearly this is the Assumption too

Which one of the following is an assumption the argument requires?

A) Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them with nozzles of equal lengths.
we require nozzles of both types and difficulty is not being talked of.

B) At some point during their ascents, all rockets will pass through the thin upper atmosphere.
Correct


C) A rocket with only short nozzles on its engines cannot reach high altitudes.
More efficient is the word and not that the short nozzle cannot cross upper atmosphere

D) For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding atmosphere throughout the rocket's ascent.
This is already given in para

E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.
again cannot be an assumption

B


I understand why B is correct and chose but the problem took me a bit of time because I wasnt able to conclusively eliminate OPTION E. Could you elaborate why E is wrong?

IMO, the problem with E is that it says that the short and long nozzles must be in a single engine. However, the stimulus says that "all rockets must have both short nozzles and long nozzles on their engines" . It could be that one engine has a short nozzle, while another engine has a long nozzle.
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E states:

Quote:
E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.

So a particular engine needs both a short nozzle and a long nozzle. Well, why can't we have two engines?! We don't necessarily need to have both nozzles on one engine. E doesn't close the gap in the argument.

B tells us exactly what we're looking for. If we're concluding that all rockets need both short nozzles and long nozzles, we need to make use of both.
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If you could shed a bit of light on why E wouldnt be the answer

Quote:
Rocket engines are most effective when exhaust gases escape from their nozzles at the same pressure as the surrounding atmosphere. At low altitudes, where atmospheric pressure is high, this effect is best produced by a short nozzle, but when the rocket passes through the thin upper atmosphere, a long nozzle becomes more effective. Thus, to work most effectively throughout their ascents, all rockets must have both short nozzles and long nozzles on their engines.

Which one of the following is an assumption the argument requires?

A) Equipping a rocket's engines with both short and long nozzles is not significantly more difficult than equipping them with nozzles of equal lengths.

B) At some point during their ascents, all rockets will pass through the thin upper atmosphere.

C) A rocket with only short nozzles on its engines cannot reach high altitudes.

D) For a rocket to work effectively, its engines' exhaust gases must leave the nozzles at the same pressure as the surrounding atmosphere throughout the rocket's ascent.

E) For a rocket to work most effectively at both low and high atmospheric pressures, it must have at least one engine that has both a short nozzle and a long nozzle.

The reason is only that it tries to limit the scope of engine requirement which eventually loses the focus that argument concentrates upon. The number of engine is a moot point to discuss here. It takes you nowhere.
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A)- Difficulty in equipping is irrelevant , we are concerned with effectiveness.

C)- again does not say short or long nozzle we are concerned with the most effective way so irrelevant.

D)- it is a supporting information given to explain a concept or support their argument not an assumption.

E)- out of scope does not talk about how many engines or their placement.

B)- CORRECT - what if some rockets do not need to pass the thin atmosphere and thus do not need the low compression long nozzle , in other words that particular rocket's most effective design would be just the short nozzle.

Key here is to focus on conclusion and the core that is effectiveness.

Thanks for reading, hope i helped ,open to answer queries.

LSAT questions are so crisp and satisfying to solve.
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