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How do I create a projectile motion function with the input of angle which is scalar, and time which is a vector.

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Martin Lacza
Martin Lacza on 24 Oct 2016
Edited: Surik Ahmed on 26 May 2021
function [x,y]=trajectory(a,time)
x0=0
y0=0
k=0
angle=a*(pi./180)
v=70
g=9.81
t=0:0.1:time
x=x0+v*cos(angle)*t;
y=y0+v*sin(angle)*t-(g*t.^2)/2
figure
plot(x,y)
end
So far I have this code, which succesfully plots the graph of a projectile at the given velocity (v) and constant (g) The input is (a) which is angle and (time) which is the amount of seconds after launch. I got stuck here because in the input (a) has to stay a scalar but (time) has to be a vector, so I can input more values for time, and the output would be more graphs with the same (a) angle, but in different times since the launch.
How can I make (time) a vector and have more plotted graphs as the output?
  2 Comments
Image Analyst
Image Analyst on 24 Oct 2016
time is the name of a built-in function so you should not use it as the name of your variable. Call it totalTime or elapsedTime or timeOfFlight instead.

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Accepted Answer

Jan
Jan on 24 Oct 2016
Edited: Jan on 24 Oct 2016
You can move the commands for creating the diagram from the function to the caller:
function main
figure;
AxesH = axes('NextPlot', 'add');
time = 20;
[x,y] = trajectory(10, time)
plot(x, y, 'r', 'Parent', AxesH)
[x,y] = trajectory(20, time)
plot(x, y, 'b', 'Parent', AxesH)
end
function [x,y]=trajectory(a,time)
x0=0;
y0=0;
% k=0 ???
angle=a*(pi./180)
v=70;
g=9.81;
t=0:0.1:time
x=x0+v*cos(angle)*t;
y=y0+v*sin(angle)*t-(g*t.^2)/2;
end
You can vary the angle in a loop also. And if you really want to vary the time, this can be done equivalently.

More Answers (1)

Image Analyst
Image Analyst on 20 Nov 2016
Edited: Image Analyst on 4 May 2020
OK, now that your homework problem is well over, here is my solution. Granted, it's a bit fancier than a typical beginner would do, but I'm an overachiever.
It computes just about everything that you could possibly want to know about the trajectory for a single angle. Then it computes and plots trajectories for several angles. You can delete anything that you don't need to know to make it simpler. The code is extremely well commented so you should have no trouble following it.
The projectile.m file is attached below these two images that it creates. If you like it, please "Vote" for my answer.
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