Re: Is this solvable using Mathematica?
- To: mathgroup at smc.vnet.net
- Subject: [mg99117] Re: Is this solvable using Mathematica?
- From: dh <dh at metrohm.com>
- Date: Mon, 27 Apr 2009 05:25:13 -0400 (EDT)
- References: <gsuiqn$dq8$1@smc.vnet.net>
Hi,
this system of equations is under determined. You have a second order
DEQ in a, what needs 2 equation and 1 first order DEQ in b, what needs
another equation. Therefore, you will need 3 equations.
Daniel
johnboy98105 at yahoo.com wrote:
> Supposed you want to define a second order derivative along with your
> ODEs. (So you can scale the second order term)
>
> Example shown below.
>
> k1 = 1;
> r1 = 1;
> NDSolve[{a'[t] == k1 b[t] - d, a''[t] == r1 b'[t], a'[0] == 0, a[0] ==
> 1, b[0] == 0}, {a[t], b[t]}, {t, 1, 10} ]
>
> But I get an error.
>
> NDSolve::ntdvmm:
> Cannot solve to find an explicit formula for the derivatives. NDSolve
> will try solving the system using a mass matrix method.
>
> NDSolve::ndnum: Encountered non-numerical value for a derivative at t
> == 0.`.
>
> Maybe this is more of a math question than software. But I would be
> very interested in seeing if it's doable in Mathematica.
>
> Thanks in advance.
>
>