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Homework Help: Problem on specific gravity

  1. Aug 22, 2009 #1
    A sunken steel ship has a mass of 500,000 kg. It is filled with water. In order to lift the ship, air bags are to be inflated inside the hull. What volume of air is needed if 7.8 is the specific gravity of steel?

    A- 436 m^3
    B- 2778 m^3
    C- 1266 m^3
    D- 872 m^3
    E- 225 m^3

    so since the specific gravity is 7.8, the density of steel is 7800 kg/m^3. but i don't know what to do next. how do you find the volume of air? i tried making the force of air pushing up equal to the force of the ship pulling down so that (density of air)(volume of air) = (density of steel)(volume of steel) but i get the volume is none of the choices above. please help.
  2. jcsd
  3. Aug 22, 2009 #2


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    Mass of the ship and density of steel is given.
    Find the volume of the ship.
    This volume and the volume of the balloon will be the volume of the displaced water.
    Weight of the displaced water must be equal to the weight of the ship.
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