function dy = dcOsc(t,y)
g = 0.01;
k = 19;
l = 0.58;
m0 = 0.115;
q = 0.1;
m = m0.*((1-q.*t).^2);
M = 0.35;

A = [0 0 1 0; 0 0 0 1; -1.*(g./l + k./M) k./M 0 0; k./m -1.*(g./l + k./m) 0 0]; 

dy = A*y;