# help-While and for loops

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Maria Andersson on 31 Jan 2014
Edited: Mischa Kim on 31 Jan 2014
Hi! I have a question about using the for and while loops to simulate a toy rocket path. The rocket will follow three steps, where in the first it is shot up in the air and will accelerate with the force (F) 16N until t=0.15 Seconds, the second step is where the rocket motor will turn of and a parachute will be fold out and the rocket will continue upwards and afterward turn to fall downwards with a constant velocity of 20m/s (-20 m/s) , the third step is when the rocket no longer will accalerate and will start from the point where the speed reaches -20 m/s until the rocket falls to the ground.
here are the three functions to use for the assignment:
v(t)= v+a*(t-t0);
h(t)=h0+v0*(t-t0)+0.5*a*(t-t0)^2
a=((F -m*g)/m
where m=0.05 kg
g=9.81
as step 1 is the startup point:
v0=h0=t0=0
Step 2:
v0 = the final speed for step 1 (v0 is max v for step 1 as step 2 starts when step 1 ends)
h0= the final speed for step 1
t0= 0.15
as no force will be current in this step, F=0 --> a= -9.81
Step 3:
v0= the end speed for step 2 which in this case is -20 m/s
t0= the end time of step 2
h0= the final hight of step 2
as no acceleration is current in this step F=mg --> a=0;
So with this information, the required assignment is to plot the whole path of the rocket by using if-sets and (or) for and while loops.
I have tried to use the for and while loops but I always have problems as I am not sure how to save the speed and height of each step in a matrix, so I really need help and it would be great if anyone could solve this problem for me asap!!
this is how my coding looks like:
m=0.05;
g=9.81;
dt=0.01;
%FOR STEP ONE:
t0=0;
tend=0.15;
h0=0;
v0=0;
F=16;
t=t0:dt:tend;
y=1:length(t);
for i=y
a=acceleration(F,m,g);
a1=a;
v=speed(v0,a1,t,t0);
h=hight(h0,v0,t,t0,a1);
end
plot(t,v,t,h)
hold on
%STEP TWO
Velocity2=[];
hight2=[];
while v>=-20
v0=max(v1);
h0=max(h1);
F=0;
a=acceleration(F,m,g);
t0=0.15;
v=Velocity(v0,a,t,t0);
Velocity2=[Velocity2;v];
h=hight(h0,v0,t,t0,a2);
hight2=[hight2;h];
t=t0+dt;
plot(t,v,t,h)
end
%STEP 3:
while h>=0;
a=acceleration(F,m,g);
v=Velocity(v0,a,t,t0);
h=height(h0,v0,t,t0,a);
t=t0+dt;
end
plot(t,v,t,h);
hold off
Azzi Abdelmalek on 31 Jan 2014

Mischa Kim on 31 Jan 2014
Edited: Mischa Kim on 31 Jan 2014
Simply save the speed and height data points into vectors:
...
for ii = 1:length(t)
...
v(ii) = speed(v0, a1, t(ii), t0);
h(ii) = hight(h0, v0, t(ii), t0, a1);
...
end
...
asumming that functions speed and hight are defined and working.