Re: System of two equations of ODE2

[Marco Atzeri]

On 12/24/2014 9:01 AM, ben wrote:
> Hi!
>
> Thanks for the answers.
>
> The sistem is 2 ODE, whit four initial conditions.
>
> I make this program but it doesn't work.
>
> <http://octave.1599824.n4.nabble.com/file/n4667923/dsf.png>

1st rule, don't paste image.
It make difficult for us to reply.

the Equation in clearly of second grade as

acceleration=d(velocity)/dt=d2(space)/dt2=-Fgravity/mass

> The vector of initial conditions i correct like that? o i have to do
>
> x0=zeros(1,4);
>
> X0(1)=G+h
>
> x0(2)=0
>
> X0(3)=0
>
> x0(4)=vo
>
> i don't know how tho make it.

as the four variables are
x,y,vx,vy

you can define f as
[dx/dt, dy/dt, d(vx)/dt,d(vy)/dt] =[ vx, vy, -Fx/mass, -Fy/mass]


> And another problem i want to plot (x,y), the position vector but it draws
> something estrange...
> Thanks.

Regards
Marco