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Homework Help: Intro to Physics: Fluids

  1. Nov 19, 2007 #1
    I have solved this problem but am not sure where I'm going wrong here...

    Suppose you pour water into a container until it reaches a depth of 20cm . Next, you carefully pour in a 9.7cm thickness of olive oil so that it floats on top of the water.

    What's the pressure at the bottom of the container? Express anser using two significant figures.

    P-P_atm= ? Pa

    P_1= P_atm + (rho)(g)(h)
    = 1.013 x 10^5 Pa + (920kg/m^3)(9.81m/s^2)(0.097m)
    = 102175.44 Pa

    P=P_1 + (P_water)(g)(h)
    = 1.013 x 10^5 Pa + (1000kg/m^3)(9.81m/s^2)(0.20cm)
    = 104137 Pa

    I keep getting this answer wrong.. I do not know what I am doing wrong. Please help!
    I've tried already 1.04x10^5
    and the above exact number.
  2. jcsd
  3. Nov 19, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The pressure at the bottom is the sum of:
    - atomospheric pressure
    - pressure due to .097 m of olive oil
    - pressure due to .20 m of water
  4. Nov 20, 2007 #3
    Thanks! I have discovered what I did wrong...I was not supposed to include atmospheric pressure in the first place. Thank you, Doc Al.
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