Results 1 to 2 of 2

Thread: solving 2nd order PDE

  1. #1
    Newbie
    Joined
    May 2011
    Posts
    1

    solving 2nd order PDE

    Need to solve for dx/ds in the following equation, keeping dy/ds.

    d^2x/ds^2 - (2/y)(dx/ds)(dy/ds) = 0

    I can just rearrange to get:

    dx/ds = (y/2)(ds/dy)(d^2x/ds^2)

    But, this is not clean to use for some later calculations.

    Is there any way to solve for dx/ds by integration?I would like an expression with dx/ds = f(y,s)
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Danny's Avatar
    Joined
    Dec 2008
    From
    Conway AR
    Posts
    2,311
    Thanks
    4
    First off, this is and ODE since there are only ordinary derivatives here. If you write your ODE as

    \dfrac{\dfrac{d^2x}{ds^2}}{\dfrac{d x}{d s} }= 2 \dfrac{\dfrac{dy}{ds}}{y}

    You can integrate giving

    \ln \dfrac{d x}{d s}} = 2 \ln y + \ln c

    or

    \dfrac{dx}{ds} = c y^2
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving 1st order ODE
    Posted in the Differential Equations Forum
    Replies: 2
    Last Post: October 8th 2011, 05:20 PM
  2. 3rd-order to first order ODE and solving
    Posted in the Differential Equations Forum
    Replies: 0
    Last Post: December 1st 2010, 12:04 PM
  3. Solving this First-Order ODE
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: September 29th 2010, 03:02 PM
  4. Need help solving some 2nd order DEs
    Posted in the Differential Equations Forum
    Replies: 2
    Last Post: August 14th 2009, 01:48 PM
  5. Solving this second order?
    Posted in the Calculus Forum
    Replies: 4
    Last Post: February 15th 2008, 10:40 PM

Search Tags


/mathhelpforum @mathhelpforum