function falling
clear all
global mass gravity alpha
mass=80;
height=600; %initial height
gravity=9.81;
tsplit=5; %time before chute opens
alpha=1/15; %drag parameter (before chute opens)
trange=[0 tsplit];
inits=[height,0]; %iniital conditions (y and v)
[t,y]=ode45(@fallfunc,trange,inits);
alpha=4/15; %drag parameter (after chute opens)
trange=[tsplit 2.85*tsplit];
inits=[y(end,1) y(end,2)]; %Use results of last run to start next
[t2,y2]=ode45(@fallfunc,trange,inits);
plot(t,y(:,1),t2,y2(:,1),'r',t,y(:,2),'--b',t2,y2(:,2),'--r','LineWidth',2)
xlabel('time (s)')
ylabel('x (m)     v(m/s)')
legend('height-before', 'height-after', 'velocity-before', 'velocity-after')
hold on
x=[0 t2(end)];
z=[0 0];
plot(x,z)
%
function z=fallfunc(t,y)
global mass gravity alpha
z=zeros(2,1);
z(1)=y(2);
z(2)=-gravity+alpha/mass*y(2)^2;