What is the question asking?

[carbonfishbone]

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Kaplan FL #8, Q10.

Which of the following is LEAST likely to be the only explanation for the difference detected in the speeds of the waves?



I am just wondering what this is asking for.

To me, it sounds like it is asking for a question the is dependent on something else. Meaning, which answer choice would dependent on another explanation for why there is a difference in speeds. However the answer choice, reasons this question as to which one is independent of other answer choice, ie which answer on its own explains the difference.

Shouldn't this question say "MOST likely", to be in line with the reasoning of the answer explanation?

Answer explanation: Recall that the speed of the wave depends on ρ, μ, and B. Reading the question stem carefully reveals that we want to find which answer choice will independently explain the difference in wave speed. The surface wave has a smaller speed than the core wave (see paragraph 2): A smaller shear or bulk modulus or a larger density could explain a decreased wave speed. Likewise, a larger shear or bulk modulus or a smaller density would explain an increased wave speed in the core wave. Choice (C) is the correct answer. Temperature has not been discussed in the passage – eliminate choice (D).

 

[0Complications]

Kaplan FL #8, Q10.

Which of the following is LEAST likely to be the only explanation for the difference detected in the speeds of the waves?

To me it sounds like it's asking for 1 factor that would contribute to a difference. If an answer gave 2 or more factors, I would also consider it as long as it supported the general theme of the question stem.

Basically, this question says (as I read it); Which of these does not cause a difference (or would seldom, if ever cause a difference)?

I'm not sure if that makes sense. I've had a few cocktails, so it's how I would read it now. ha ha.

 

[robrobbberts]

Can you post the full question? That sounds so strange. :/

 

[carbonfishbone]

Yea sure I'll post the whole problem. 0complication, I still don't see how its asking for 1 factor. If you change LEAST to MOST, then I can see its asking for 1 factor. But since its least, I would assume its the opposite of MOST.

From the answer choices, C is the only one that would explain a higher wave speed on the surface. The rest would indicate a slower speed, meaning something else would have to be the cause of the faster speed.

The full question:

10. A seismometer detects a wave that passes through the
Earth's surface and another that passes through the
Earth's core. Which of the following is LEAST likely
to be the only explanation for the difference detected
in the speeds of the waves?
A. The surface rock may have a smaller bulk modulus.
B. The surface rock may have a larger density.
C. The core rock may have a smaller shear modulus.
D. The core rock may have a lower temperature.


Useful information from the passage:

Variations in the speed at which seismic waves propagate
through the Earth can cause variations in seismic
waves recorded at the Earth's surface. By measuring these
variations, geologists can gain information about the composition
of underground structures. Longitudinal seismic
waves travel at speeds from about 6 km/sec in surface rock
to about 10.4 km/sec near the Earth's core. The speed of
these waves (v) in solids, liquids, or gases depends on several
factors as shown in Equation 1, including the density
of the medium (p), its shear modulus (u), and the bulk
modulus of the media (B). Any change in rock or soil property
that causes p, u, or B to change will cause seismic
wave speed to change.

Then the equation:

V=Sqrt((((4/3)u + B) / p ))

 

[robrobbberts]

Ah, I see it!

C. The core rock may have a smaller shear modulus.

look at the equation:


v=Sqrt((((4/3)u + B) / p ))


A smaller shear modulus would mean a smaller velocity.. But, the passage states that waves traveling through core rock travel at a faster velocity than waves traveling at the surface. C is the answer because it gives a false reasoning. D wasn't even mentioned in the paragraph, so it can be true or false, you don't know. The question is basically asking which choice is False.