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Homework Help: Density and Boyancy

  1. Nov 19, 2009 #1
    1. The problem statement, all variables and given/known data

    apparent mass of the metal weight in air = 100g
    apparent mass of the metal weight in water = 75g

    a)Compute the buoyancy force. From this, compute the volume of the metal. Compute the density of the metal. The density of aluminum is 2.7 g/cm3, of iron is 7.9 g/cm3, and of gold is 19.3g/cm3. Is your metal mostly aluminum, iron, or gold?

    b)The mass of a plastic sphere is 110g. Calculate the buoyancy force and use it as above to compute the

    3. The attempt at a solution
    F bouyancy = density water * vmetal*g
    Fbouyancy = Mdw*g

    Fbouyancy = (Mmetal in air - Mmetal in water)
    Fbouyancy =( 100-75)(9.8) = 245g*m/s^2
    F bouyancy = density water * vmetal*g
    245g*m/s^2 = 1g/cm^3 *Vmteal*9.8m/s^2
    Vmetal = 25cm^3
    p = m/v
    p = (100g/25cm^3)
    I not too sure if this is correct.....
    I dont know how to do part b)
    Last edited: Nov 19, 2009
  2. jcsd
  3. Nov 19, 2009 #2


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    Homework Helper

    Your result is correct.

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