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

Homework Help: Simple question - barometric formula derivation

  1. Mar 8, 2010 #1
    I haven't had extensive experience in solving DE's just yet; I'm curious as to where the P(0) term comes from between the 4th and 5th expressions in the following derivation:

    http://en.wikipedia.org/wiki/Barometric_formula#Derivation

    My attempt follows:

    [itex]\frac{dP}{P} = - \frac{M g\,dz}{kT}[/itex]

    [itex]\int\frac{1}{P}dP = - \int\frac{M g}{kT}dz[/itex]

    [itex]P = e^{-\int\frac{M g}{kT}dz}[/itex]

    [itex]P = e^{-Mgz/kT}[/itex]

    Clearly I'm missing something obvious, but I don't know what exactly.
     
  2. jcsd
  3. Mar 9, 2010 #2
    Limits of the integration.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook