1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Density of sea water

  1. Nov 17, 2009 #1
    What the density of sea water at depth of 1000 M where the water pressure is about 1.0*10^7 pascal the density of sea water at the surface is 1.03*10^3 kilograms per cubic M?

    2. Relevant equations
    B of water=,21*10^10 n/m^2
    it is approx to the bulk of sea water

    3. The attempt at a solution
    Ihave used the (1000m)depth as aforce at the bottom then A=f/p=1000/1.0*10^7=10^-4 M^2
    dV=A*h=10^-4*1000=10^-1 m^3
    from bulk modulus=dp/dv/v=,21*10^10=10^7/dv/v then dv/v=4,76*10^-3 then v(surface)= x then density surface=mass/v then mass = x then v depth = dv+v surface(because as account to the bulk modulus the volume smaller at the depth) then the density of the depth= mass/v depth

    it right to assume that the depth is aforce??????
    Last edited: Nov 17, 2009
  2. jcsd
  3. Nov 17, 2009 #2


    User Avatar
    Homework Helper

    no, depth is not a force, depth is a distance

    a supported column of fluid in a gravitational field leads to a hydrostatic pressure (which has units of Force/Area)

    the hydrostatic pressure in a constant gravitational field, is given by
    [tex] P = \rho g h [/tex]
    where h is the depth
  4. Nov 17, 2009 #3
    thank you for help but g is the acceleration due gravity ?what p
    can you help me mor is there another method ?but I have to use the bulk modulus in the solution I will be very grateful for your help

    thank you alot
    Last edited: Nov 17, 2009
  5. Nov 17, 2009 #4


    User Avatar
    Homework Helper

    g is the accleration due to gravity

    so, first calculate the pressure at 1000m assuming the density is constant

    then assume the bulk modulus is constant with pressure & calculate the corresponding volume & density change. (similar to what you attempted previously)

    This will be a pretty good approximatino to the densety change, to do any better you would have to set up an integral
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook