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Homework Help: Archimedes Principle and Specific Gravity Determination

  1. Jan 7, 2010 #1
    1. The problem statement, all variables and given/known data
    a crown that is supposed to be pure gold has a mass of 850g. Its apparent mass when immersed in water is 798g. (a) what is the volume of the crown? (b)is it pure gold?If not, what is the percentage by volume of gold in the crown assuming that the crown is an alloy of lead and gold?


    2. Relevant equations
    density = m/v
    specific gravity = weight of object in air /weight of object in air - weight of object immersed in water
    density of gold = 19300kg/m^3
    density of lead = 11300kg/m^3


    3. The attempt at a solution
    converted 850g to kg. 850g/1000g=.85kg
    converted .85kg to weight. .85*9.8m/s^2=8.33 newton
    converted 798g to kg. 798g/1000g = .798kg
    converter 798kg to weight. .798*9.8m/s^2=7.8204
    used specific gravity
    sp gr= 8.33N/8.33N - 7.8204N
    cancel newton
    16.34615
    since specific gravity is numerically equal to 1g/cm^3 in cgs system
    16.34615*1g/cm^3 = 16.34615g/cm^3

    converted 16.34615g/cm^3 to kg/m^3

    16.34615g/cm^3 = 16346.15kg/m^3

    density of crown = 16346.15kg/m^3

    i don't know what's next...
    i don't even know if i'm on the right track...
     
    Last edited: Jan 7, 2010
  2. jcsd
  3. Jan 7, 2010 #2

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    I think you are making it a little unecessarily complicated.

    The difference in weight is equal to the mas sof water it displaces.
    So it weighs the equivalent of 850-798g of water
    And water has a density of 1g/cc, so it has a volume of how many cc ?
     
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