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

Differential equation

  1. Dec 14, 2011 #1
    [tex]\frac{ds}{dt}=600-\frac{2s}{200+t}[/tex]

    [tex]\frac{ds}{dt}+\frac{2s}{200+t}=600[/tex]

    [tex]\frac{ds}{dt}e^{ln(100+t/2)}+\frac{2s}{200+t}e^{ln(100+t/2)}=e^{ln(100+t/2)}600[/tex]

    [tex]\frac{d}{dt}(se^{ln(100+t/2)})=(100+t/2)600[/tex]

    [tex]se^{ln(100+t/2)}=\int(100+t/2)600dt[/tex]

    [tex]s(100+t/2)=600(100t+t^2/4)+C[/tex]

    t=0 s=20 000

    [tex]20.000\cdot100=C[/tex]

    But this is wrong

    I guess i want to know what I did wrong. I used the product rule for derivation backwards. Here is answer sheet

    http://bildr.no/view/1051423
     
  2. jcsd
  3. Dec 14, 2011 #2

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    The integrating factor is wrong. Revise your calculation and look up the formula for it in the book.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...