#19 - When an ordinary piece of steel is put under pressure

[LSAT2018]

I couldn't find an answer for this question because I was trying to base the answer on the statement in the stimulus that the glass volume remains unchanged.
How answer (E) correct?

[Shannon Parker]

I couldn't find an answer for this question because I was trying to base the answer on the statement in the stimulus that the glass volume remains unchanged.
How answer (E) correct?

I can see where that got confusing. Although answer choice E does not specifically state that the overall volume of the glass will remain unchanged, it describes what will occur, and does not indicate that the volume will change so it does not violate the rule.

Glass is fluid, so it flows away from the pressure. If you place heavy object in the middle of the glass it will create pressure. The glass will flow away from the heavy object making that portion of it thinner. The overall volume of the glass remains unchanged during this process.

Hope this helps.
Shannon

[lsat_novice]

I don't understand why A is incorrect. Because glass is fluid, I figured it would have to be of uniform thickness. "A" says the glass becomes larger in size yet is still uniform in thickness. In order for the volume to remain the same (as required by the stimulus) the glass could be larger in size and thinner in thickness.

[Adam Tyson]

The heavy object is being placed in the center of the sheet of glass, and so the glass under it will flow away from it to the edges that are not under pressure. The problem with answer A is "uniform" - what evidence is there that the entire sheet of glass will be the same thickness everywhere, at the center and at all the edges? It will certainly get thinner at the center, but it could then get thicker just beyond the area where the heavy object is sitting. Picture a cookie sheet filled with pudding, and place a cup in the center - the pudding moves out from under the cup, and the other areas of the cookie sheet rise up. Not uniform thickness, but just the opposite!

Is it possible that the glass will get larger and remain of uniform thickness? Perhaps, but that seems less likely than some parts getting thicker, just outside the range of the heavy object, while remaining at or close to the original thickness out at the edges. With little pressure on the rest of the glass there isn't anything forcing it to flow. The stimulus did say that the portion under pressure will flow, and it also said the flow is to areas under less pressure. Less pressure means less flow, presumably. Less flow means less change. We will end up with a distorted thickness rather than uniformity.

[bella243]

Is this a must be true question?

[Adam Tyson]

Since it is our task to draw a conclusion, or to make an inference, I think it is safe to call this question a Must Be True (really it's softer variant, Most Strongly Supported, because of the words "most logically" in the stem.) Whenever you are asked to use the facts in the stimulus to support an answer choice, you are looking at a version of a Must Be True question. Well spotted, bella243!