funcprot(0)
function dxdt=fu(t,x,m,A1,A2,K1,K2)
    dxdt=zeros(4,1);
    dxdt(1)=x(2);
    dxdt(2)=1/m(x(3)*A1-x(4)*A2);
    dxdt(3)=K1*t;
    dxdt(4)=K2*t;
endfunction

r1=0.03;
r2=0.02;
pi=3.141562;
A1=pi*r1^2;
A2=A1-(pi*r2^2);
K1=5000;
K2=10000;
m=450;
x0=0;
t0=0.1;
t=0.1:0.001:5;

sol = ode(x0,t0,t,fu)

plot(t,sol)