% EA3
%Spring-block system with no damping or friction

clear all;
close all;
disp('Undamped spring-block system');
%parameters (mass; spring constant;)
m	=	40;			%mass of block
K	=	10;			%spring constant

%
% Initial conditions
i	=	1;				%time index
rx(i)	=	.2;			%initial position
vx(i)	=	0;			%initial velocity

%time parameters
start_time = 0;
dt=input('Enter time step:');
%dt	=	.1;			%time step
final_time	=	100;
time(i)	=	start_time;	% let us keep a vector of times for plotting
%
%
% Integrate equations of motion
for t = start_time:dt:final_time
	a	=	-(1/m)*(K*rx(i));		%current acceleration
	vx(i+1)	=	a*dt+vx(i);			%calculate next velocity
	rx(i+1)	=	vx(i)*dt+rx(i);		%calculate next position
	time(i+1)	=	time(i)+dt;
	i	=	i+1;
	end
%
%Plot the path
comet(time,rx)
pause
subplot(2,1,1)
plot(time,rx), title('Spring-block oscillator-position'),xlabel('Time'),grid
subplot(2,1,2)
plot(time,vx), title('Spring-block oscillator-velocity'),xlabel('Time'),grid