Pressure in a Lake: Find Depth for 4.5 atm

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Homework Help Overview

The problem involves determining the depth in a freshwater lake where the water pressure reaches 4.5 atm, given that the surface pressure is 1 atm. The context is centered around fluid pressure and the relevant equations for calculating pressure at a certain depth.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the method of calculating depth using the pressure difference and the importance of unit conversion to pascals. There is also a consideration of the relationship between depth and atmospheric pressure.

Discussion Status

Some participants have provided guidance on ensuring proper unit conversion and have confirmed the original poster's method appears correct. There is ongoing exploration of the assumptions regarding pressure and depth relationships.

Contextual Notes

Participants note the necessity of using consistent units, particularly the density of freshwater in kg/m³, and question whether the original poster has correctly applied these conversions in their calculations.

Manda_24
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Homework Statement


At the surface of a freshwater lake the air pressure is 1 atm. At what depth under water in the lake is the water pressure 4.5 atm?

Homework Equations


P=a+hgp
h=(P-a)/(g*p)

The Attempt at a Solution


h=(4.5x105 - 1x105)/(9.8*1000)=35.71
I also did the equation with 9,000 Pa converted to atm, which I think it what I'm supposed to do but I still get the incorrect answer.
 
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Convert everything to pascals before using the equations. Also, be sure that the density you have for freshwater is in kg/m3. I'm not seeing anything wrong in your method, so I'm assuming the problem is in the units.
 
"h=(4.5x105 - 1x105)/(9.8*1000)=35.71" Appears to be correct. If I am not mistaken, 10 m of water is roughly = to 1 atm. But, I am not 100% sure off the top of my head. If that's the case, it would make sense that 35 m of water would be about 3.5 atm plus the 1 atm from the atmosphere = 4.5 atm.

If you know, what is the answer supposed to be?
 
Gear300 said:
Convert everything to pascals before using the equations. Also, be sure that the density you have for freshwater is in kg/m3. I'm not seeing anything wrong in your method, so I'm assuming the problem is in the units.

Thanks, I just needed to convert the top to pascals, I thought I only had to do it to the bottom.
 

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