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Homework Help: Mass of earths atmosphere

  1. Sep 25, 2010 #1
    1. The problem statement, all variables and given/known data


    above each square ince of the earths surface is 14.7 pounds of air. the density of air at sea level is 1.27g/l. the earth is 7930 miles in diameter and has a mass of 5.98x10^24kg.

    use this data to determine the mass in kg of the earths atmosphere

    determine the average density in g/mm

    2. Relevant equations
    4pieR2


    3. The attempt at a solution
    14.7 lb air/in2 x 1kg/2.205lb x (39.37in/1m)2=1.03x10'4/m2 air above surface
    then
    A=4pieR2=1.97x10'8mi2 x (1km/.6214)=5.11x10'14m2

    then multiply the answers for 1.534x1017kg

    is that close for the "a" part?

    thanks
     
    Last edited: Sep 26, 2010
  2. jcsd
  3. Sep 25, 2010 #2

    D H

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    No.

    Which are your symbols, and what is all this addition stuff?

    Note: the "pounds" per square inch is a unit of force, not mass.
     
  4. Sep 26, 2010 #3
    sorry typed it wrong. i reposted my work. i don't know where else to go
     
  5. Sep 26, 2010 #4

    D H

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    I'll be a bit more explicit in where you went wrong.

    The "pounds" in "pounds per square inch" is a unit of force, not mass. Your mistake results from assuming it is a unit of mass.
     
  6. Sep 26, 2010 #5
    ok thanks. i'll try to look up the difference b/c we have not covered this distinction in class
     
  7. Sep 26, 2010 #6
    14.7psi x 702771g/m2 x 1kg/1000g= 10331kg/m2 of air above surface
    A=4pieR2=1.97x10'8mi2 x (1km/.6214)=5.11x10'14m2 surface area

    5.29x10'18 mass of atmosphere!?
     
  8. Sep 26, 2010 #7

    D H

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    Looks good, but where did you come up with 702771g/m2?
     
  9. Sep 26, 2010 #8
    I looked it up the conversion. I thought it might be in the problem but I can'tseem to find it working backwards
     
  10. Sep 26, 2010 #9
    Volume of a sphere?? Does it have to do with density
     
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