Gauge Pressure

[anondukie]

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“Objects A and B are submerged at a depth of 1 m in a liquid with a specific gravity of 0.877. Given that the density of object B is one-third that of object A and that the gauge pressure of object A is 3 atm, what is the gauge pressure of object B? (Note: Assume atmospheric pressure is 1 atm and g = 9.8 m/s^2)”

Excerpt From: Kaplan. “Kaplan MCAT Physics and Math Review: Created for MCAT 2015 (Kaplan Test Prep).” iBooks.

^ I understand that the gauge pressure in both cases will be the same because the density of the fluid and the depth are both equal. However, I'm not sure how they arrived at a gauge pressure of 3 atm using the data provided. I know that the gauge pressure calculation is irrelevant in this particular instance but I'm just curious! Did they just not bother to ensure that the numbers actually work? I apologize for being paranoid!

Thanks!

 

[aldol16]

Yeah, that does seem strange. So your gauge pressure here is simply density times g times height of column of water. Which means 0.877(1000 kg/m^3)(9.8 m/s^2)(1 m) = 8595 kg/m*s^2 = 8595 N/m^2 = 8595 Pa. Which is wayyyyy less than 1 atm.

 

[anondukie]

Exactly! I guess they just weren't paying attention. Thanks for double checking!

 

[aldol16]

Lol if they were correct, then it would be very bad for water. If the pressure is 3 atm only 1 m below the surface of a fluid that is less dense than water, then it would be even more for water. Which means that swimming could get difficult.