Path: news.mathworks.com!not-for-mail From: "Sridatta Pasumarthy" <sridatta1988@gmail.com> Newsgroups: comp.soft-sys.matlab Subject: Solving second order differential equations Date: Thu, 25 Nov 2010 16:48:04 +0000 (UTC) Organization: IIT Delhi Lines: 22 Message-ID: <icm404$2pn$1@fred.mathworks.com> Reply-To: "Sridatta Pasumarthy" <sridatta1988@gmail.com> NNTP-Posting-Host: webapp-05-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1290703684 2871 172.30.248.35 (25 Nov 2010 16:48:04 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Thu, 25 Nov 2010 16:48:04 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 2616662 Xref: news.mathworks.com comp.soft-sys.matlab:690000 Hi, How do i solve four differential equations of second order involving many variables (numerically)? I have referred van der pol (non-stiff) example in Matlab, but it didn't help much because i couldn't figure a way to convert these to first order right away. Please help me find a solution. Problem Structure ---------------------------------- w' = [k*f(z)] * y' w * x'' = c*g(z) * y' w * y'' = f(z) + g(z) * x' + j(z) * z' w * z'' = c*j(z) * y' 1-(1/sqrt(w))=x'^2 + y'^2 + z'^2 x(0)=0, y(0)=0, z(0)=0, dx/dt(0)=0, dy/dt(0), dz/dt(0)=v c,k,v are constants. It also doesn't help that f,g,j are complicated exponential functions based upon z. I am supposed to plot 'dw/dz' vs 'z' ---------------------------------- Thanks, Sridatta