# Hydrostatics question

1. Jan 26, 2007

### srh

1. The problem statement, all variables and given/known data
An empirical formula relating pressure and density for seawater w/ temperature constant is:
p/pa = (k+1)(d/da)^7-k
pa - pressure condition on the surface
da - density condition on the surface
k - dimensionless constant
Using this formula in the hydrostatics relation, determine the pressure as a function of depth.

2. Relevant equations
Hydrostatic relation: dp/dz = -dg where d is density
T=T0-kz
d=P/RT

3. The attempt at a solution
I tried to replace d w/ P/RT and then T w/ T0-kz to get the equation in terms of z. When I tried to take the derivative it was getting very complicated and I couldn't get it to work. I think I'm just approaching the problem incorrectly. I was wondering exactly how to start this problem. I know in order to take the derivative w/ respect to z there needs to be a z in the equation.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 26, 2007

### teknodude

Why do you need to differentiate with the hydrostatic relation?