function ydot = sect_5_3_ode_fn_part_b(t,y)
% SECT_5_3_ODE_FN_PART_B - solve the ODE's from a Chandrasekhar-type system
%
% Written by:
% -- 
% John L. Weatherwax                2005-08-14
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

% some parameters:
omega_n = 10;
zeta = 0.3;
q = 10;

% extract the components:
y  = y(:); 
y1 = y(1);
y2 = y(2);
k1 = y(3);
k2 = y(4);

ydot = zeros(4,1);

ydot(1) = -k1*y1 + y2;
ydot(2) = ( -omega_n^2 - k2 )*y1 - 2*zeta*omega_n * y2;
ydot(3) = y1^2;
ydot(4) = y1*y2;