## Matlab

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terminal velocity graphing Posted by wvu12 on 24 Mar 2009 at 7:17 AM
i need to be able to plot the vertical speed and the altitude as a function of time. attached is the code. any help would be appreciated
Re: terminal velocity graphing Posted by giug on 24 Mar 2009 at 9:24 AM
I can't understand what is your problem, in your code you already plot the altitude as a function of time.
Re: terminal velocity graphing Posted by wvu12 on 24 Mar 2009 at 9:37 AM
the graph is not plotting properly and i do not know how to get it to look the right way, also need to have seperate plots for the velocity and altitude
Re: terminal velocity graphing Posted by giug on 24 Mar 2009 at 10:08 AM
If you don't explain what you mean with "plot properly" I can't help you.
To plot two different figures you can code in this way:

figure(); plot(time, altitude);
figure(); plot(time, velocity);
Re: terminal velocity graphing Posted by wvu12 on 24 Mar 2009 at 11:43 AM
the velocity graph was only using one point for the entire graph, we need it to use all the points for the velocity graph. i also can't figure out how to get the altitude to plot. attached is the revised information.
Re: terminal velocity graphing Posted by giug on 24 Mar 2009 at 12:11 PM
Can you give me some test input values so that I can check the code, because it gives me some errors and perhaps it depends on my "random" input values.
Re: terminal velocity graphing Posted by wvu12 on 24 Mar 2009 at 12:23 PM
initial altitude is 3800
parachute diameter is 10
opens at 40
time step is .1
Re: terminal velocity graphing Posted by giug on 24 Mar 2009 at 12:37 PM
Now it runs!
To plot all the velocity values you have to code in this way (I underline the lines that I have added):

figure();
while t<TO && Alt>1000
if V>-Vt_before
a=(1/2)*(pair/m)*(V^2)*Ab*Cdb-g;
V=Vi+a*TS;
Alt=Alt+V*TS+(1/2)*a*TS^2
Vi=V;
t=t+TS
time=t;
disp('The skydiver did not reach terminal velocity.')
else Vterm=1;
Alt=-Vt_before*TS+Alt
t=t+TS
disp('The skydiver reached terminal velocity.')
end
plot(t,V,'.');hold on
end
Re: terminal velocity graphing Posted by giug on 24 Mar 2009 at 12:50 PM
To plot the altitude:

figure();
while Alt>0
Alt=Alt-Vt_after*TS;
t=t+TS;
plot(t,Alt,'.');hold on
end
Re: terminal velocity graphing Posted by wvu12 on 24 Mar 2009 at 1:15 PM
thank you, we modified what you gave us to graph for the entire duration of the jump.

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