mamaol69

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15 years, 283 days

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These are answers submitted by mamaol69

I've seen this one but is it possible to have a numeric resolution with this kind of system ... because even with two equation it doesn't work.

Well, this is my code, I don't understand what's wrong in it... :s

 

> R := 0.25e-1; h := 0.275e-1; ro := 1; M := .1; C := 1; beta := evalf[10](.2*Pi*1/180); j0 := evalf[10](M*R^2); j1 := evalf[10]((1/4)*M*(R^2+(1/3)*h^2));
>
> sim1 := arccos(1-s/R)-(1-s/R)*sqrt(1-(1-s/R)^2);

> sim := subs(s = abs(z(t))/sin(evalf[10](13*Pi*1/180)), sim1);

 

eqn := diff(diff(x(t), t), t) = -ro*R*sim*((diff(x(t), t))^2+(diff(z(t), t))^2)*C*sin(beta+evalf[10](13*Pi*1/180))*sin(evalf[10](13*Pi*1/180))/(2*M), diff(diff(z(t), t), t) = ro*R*sim*((diff(x(t), t))^2+(diff(z(t), t))^2)*C*sin(beta+evalf[10](13*Pi*1/180))*cos(evalf[10](13*Pi*1/180))/(2*M)-g*R/R((diff(x(t), t))^2+(diff(z(t), t))^2)^2;

init := x(0) = 0, (D(x))(0) = 2, z(0) = 2.25, (D(z))(0) = .5;

sol := dsolve({eqn, init}, numeric, {z(t), x(t)}); sol(1);

 


Error, (in sol) global 'g' must be assigned to a numeric value before obtaining a solution

-> I don't understand what I have to do...

 

Thanks :)
 

I've already searched for it but the examples are for nonlinear equations but of the first order..

If it is a second order then there are no example of systems ...

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