Re: A simple ordinary differential equation
- To: mathgroup at smc.vnet.net
- Subject: [mg98255] Re: A simple ordinary differential equation
- From: dh <dh at metrohm.com>
- Date: Fri, 3 Apr 2009 04:40:27 -0500 (EST)
- References: <gr21kh$lpg$1@smc.vnet.net>
Hi,
look at: f[x_?NumericQ] = 1 - 1111*x'^2
you can not take the derivative of a number.
Daniel
I. Shechtman wrote:
> What is wrong with this equation?
>
> Clear[sol]
> f[x_?NumericQ] = 1 - 1111*x'^2;
> sol = NDSolve[{x''[t] + (16/10^4)x'[t]^2*Sqr[
> f[x[t]]]/x[
> t]^2 - (1458/10^9)*f[x[t]]/x[t]^2 ==
> 0, x[0] == 1, x'[0] == 0}, x[t], {
> t, 0, 100}, AccuracyGoal -> 8,
> PrecisionGoal -> 8, WorkingPrecision ->
> 30, MaxSteps -> Infinity];
> Plot[Evaluate[x'[t] /. sol], {t, 0, 100}]
>