%simple mass-spring-damper: 
global m b k  l0 f_ext;
m=2;
b=0.5;
k=50;
l0 = 1.5;

%first conditions: 
f_ext	= 
x0	= 
tspan	= 
[t_1, x_1] = 


%second conditions: 
figure
f_ext	= 
x0	= 
tspan	=
[t_2, x_2] =