Air Pressure and Water Pressure

[vrobins1]

Homework Statement

"At the surface of a freshwater lake the air pressure is 1.1 atm. At what depth under water in the lake is the water pressure 4.5 atm?"

Homework Equations

I used the equation P_gauge = Dgh

The Attempt at a Solution

I converted my atm to Pascals--> (4.5)(100000) = 450000 Pa
P_guage = Dgh
P_guage = (1000)(9.8)(h)

-I used 1000, the density of water, but I'm not sure that is the right info to use for D!

Then I solved for h.

h = 450000/ (10000x9.8)
h = 45.92
I got it incorrect though. Can anyone offer any insight? Thanks!

 

[PhanthomJay]

Homework Statement

"At the surface of a freshwater lake the air pressure is 1.1 atm. At what depth under water in the lake is the water pressure 4.5 atm?"

Homework Equations

I used the equation P_gauge = Dgh

The Attempt at a Solution

I converted my atm to Pascals--> (4.5)(100000) = 450000 Pa
P_guage = Dgh
P_guage = (1000)(9.8)(h)

-I used 1000, the density of water, but I'm not sure that is the right info to use for D!

Then I solved for h.

h = 450000/ (10000x9.8)
h = 45.92
I got it incorrect though. Can anyone offer any insight? Thanks!

That would have been OK if the problem asked for the gauge pressure. I think it's looking for the depth at an absolute pressure of 4.5 atm, which includes the atmospheric pressure.