Solving coupled 2nd order ODEs

Hi,

I am trying to solve coupled 2nd order ODEs. When one consider quadratic air resistance, equations of motion of a projectile take the form:

mx"=-cx'(sqrt(x'^2+y'^2))

my"=-mg-cy'(sqrt(x'^2+y'^2))

where x is horizontal distance and y is vertical distance.

Can this be done in Matlab? I understand, I can reduce one second order ODE to a series of first order ODEs, but how to address coupled part i.e. x'' depends on y' and y'' depends on x'.

Thanks

[Torsten]

x1' = x2

x2' = -c*x2*sqrt(x2^2+x4^2)/m

x3' = x4

x4' = -g -c*x4*sqrt(x2^2+x4^2)/m

where x1 is horizontal distance, x2 is horizontal velcocity, x3 is vertical distance and x4 is vertical velocity.

Now you can use one of the ODE solvers (ODE45, ODE15S).

[OJAS POTDAR]

Thanks. This worked nicely:

function dydt = CatchAPass(t,y,C)

dydt = zeros(4,1);

dydt(1)= y(2);

dydt(2)= -C*y(2)*sqrt(y(2)^2+y(4)^2);

dydt(3)= y(4);

dydt(4)= -9.8-C*y(4)*sqrt(y(2)^2+y(4)^2);