Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Physics modelling problem.

  1. Sep 3, 2008 #1
    so im tearing my hair out with this one...

    the density of the earth's atmostsphere vaires with height r above the earth's surface as

    p = p(o) exp(-r/r(o))

    where p(o) the density of the air at ground level, is 1.3 kg/m^3 and r(o) the scale height is 8km
    use this to estimate an approximate value for the total mass of the atmostsphere, given most of the mass lies within a ddistance above the ground that is much smaller than the radius of the earth

    R(earth) = 6.4x10^6

    So my attemot at a solution
    1) ive got that p = mass/volume so intergrating the expresion with respect to volume gives the total mass of the earth r = v^(1/3).
    then R(earth) >> r
    but then i get stuck.

    2) ive tried to divide the equation through by V but still that leaves me with
    r(earth) >> r.

    the problem is deailing with the much greater than part of r(earth) >> r, i dont know how to approach it.

    thanks guys :)
  2. jcsd
  3. Sep 3, 2008 #2
    No one even got a clue on how to solve this?
  4. Sep 3, 2008 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    What is the mass of the air that lies between a height r and a height r+dr?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook