1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tricky Integration

  1. Jun 24, 2010 #1
    1. The problem statement, all variables and given/known data

    [tex]E = \frac{e^2}{4 \pi \epsilon_0 a_0^3 } \left( - b \int_0^b e^{- \frac{2r}{a_0}} dr + \int_0^b r e^{- \frac{2r}{a_0}} dr \right)[/tex]

    I have to use these integrals,

    [tex] \int_0^x e^{-u} du = 1 - e^{-x}[/tex] and [tex] \int_0^x u e^{-u} du = 1 - e^{-x} - xe^{-x}[/tex]

    I get:

    3. The attempt at a solution

    [tex]E = \frac{e^2}{4 \pi \epsilon_0 a_0^3 } \left( - \frac{a_0 b}{2} (1 - e^{- \frac{2b}{a_0}}) + \left(- \frac{- a_0 b}{2} e^{- \frac{2b}{a_0}} - \frac{a_0^2}{4} e^{- \frac{2b}{a_0}} + \frac{a_0^2}{4} \right) \right) [/tex]
  2. jcsd
  3. Jun 24, 2010 #2


    User Avatar
    Science Advisor

    I think you blew a sign in the third term. It should be negative, not positive. Otherwise, it looks correct.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Tricky Integration Date
Tricky Integration Dec 5, 2017
Solving tricky limit (involving defined integral and sine) May 17, 2016
Tricky integral Apr 9, 2016
Tricky integration (maybe delta function) Mar 8, 2016
Tricky integral Jan 14, 2016