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Homework Help: Fluid Mechanics!

  1. Mar 15, 2009 #1
    1. The problem statement, all variables and given/known data

    A submersible with a mass of 2.75 x10^3 kg remains at a constant depth beneath the ocean surface. To make the submersible rise, 1.50 x10^2 kg of ballast is released. Ignoring friction, what is the upward acceleration of the submersible? (D = 1.025 x 10 ^3 kg/m^3 )

    2. Relevant equations

    Fb=weight-apparent weight.
    Fg/Fb=Density of object/Densitiy of fluid
    Fb=mass of fluid x gravity

    3. The attempt at a solution
    First, I tried using Fnet=Fb-Fg. I multiplied 150x9.81. I thought this would be the buoyant force. Then, i multiplied 2.75 x10^3 kg by 9.81 as well. I subtracted the two values, and then divided the given net force by the sum of two masses. I think my answers are way off. I am so lost. Don't I have to calculate the Fg of the object and then calculate the required acceleration of the buoyant force that will cancel off the Fg?
  2. jcsd
  3. Mar 16, 2009 #2


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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi hank09! Welcome to PF! :smile:
    why? :confused:

    F = ma, so what is that F? :wink:
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