clear; close all
%
%  spring-damper system
%  Homework #8
%  Joe Student
%
k = 50.e3;  %% 50 kN/m
b = 100.e3; %% 100 kN-sec/m
duration = 5;
dt = duration/200;
t = 0:dt:duration;
period = 2;
kase = 1;  amp = 0;  x0 = 0.1; name = '(none)';
%kase = 2;  amp = 1000;  x0 = 0;  name = 'sine wave';
%kase = 3;  amp = 1000;  x0 = 0;  name = 'square wave';
etc = [b k kase period amp];
[t,x] = %% call to ode45 goes here

subplot(3,1,1);
plot(t,1000*x);
grid on
ylabel('Displacement, mm');
title(sprintf('Case %d, applied force: %s',kase,name));

subplot(3,1,2)
xdot = %% call to xdot_bk goes here
Fb = b*xdot;
plot(t,Fb/1000);
ylabel('Damper force, kN')
grid on

subplot(3,1,3)
Fk = k*x;
plot(t,Fk/1000)
xlabel('Time, sec');
ylabel('Spring force, kN');
grid on