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: Question Regarding Bulk Modulus

  1. Apr 23, 2008 #1
    The deepest point in any ocean is in the Mariana Trench, which is about 11 km deep, in the Pacific. The pressure at this depth is huge, about 1.13 X 10^8 N/m^2.

    (a) Calculate the change in volume of 1 m3 of seawater carried from the surface to this deepest point.
    wrong check mark m3

    (b) The density of seawater at the surface is 1.03 X 10^3 kg/m3. Find its density at the bottom.
    kg/m3

    (c) Is it a good approximation to think of water as incompressible?
    Yes
    No

    -----------------------------

    The above is the question. Now, I didn't think I would have an issue with this, but apparently I am. The bulk modulus equation is:

    B = -ΔP/ [(ΔV/Vi)] where:
    B = bulk modulus, ΔP = change in pressure, ΔV = change in volume and Vi = initial volume.

    I am trying to find ΔV for part A (afterwards the rest should not be difficult at all).

    So ΔV = -[ΔP(Vi)]/B

    When you use 0.21 X 10^10 for the bulk modulus of water (which apparently the online assignment website wants this for water and not seawater), you get:

    ΔV = -(1.13 X 10^8)(1)/(0.21 X 10^10) = -0.0538 m^2

    I actually inputted this into the website as a positive value and it counted it as wrong. The reason this is strange is because it will normally say "wrong sign" and if it's off by 10% or less it will say so. So I am hesitant to input in the negative value because that will be my last submission. Any help is appreciated. Thanks.
     
  2. jcsd
  3. Apr 24, 2008 #2
    This can be locked, I figured out the problem.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook