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Homework Help: Calculate Bulk modulus

  1. Jan 2, 2012 #1
    1. The problem statement, all variables and given/known data

    A rock at the surface has a density of 2600kg(m^(-3)
    90000m down its density is 3100kg(m^(-3)
    Change in pressure at the depth is due to hydrostatic pressure.
    Whats the bulk modulus of the rock?

    2. Relevant equations
    Δp=p + ƿgh


    3. The attempt at a solution
    Hydrostatic pressure:
    p(90000)= 1 x 10^(5) Pa + (3100kg(m^(-3))(9.81m/s^(2))(90000m)
    Δp= 2.74 x 10^(9) Pa

    Δp= - B(ΔV/V)

    So, (ΔV/V) => ΔV=m/ƿcompressed
    And V=m/ƿintital

    So the 2 m cancel and the expression for the bulk modulus is
    B= 3.3 x 10^(9)

    I think I may have made a slight misktake please help?
  2. jcsd
  3. Jan 2, 2012 #2
    B has the right order of magnitude so I think you are fine.
  4. Jan 2, 2012 #3
    Actually i made a mistake with the Vfinal expression.
    My new answer is B= 5.3 x 10^(8)
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