Projectile motion

[anny321dum]

I am trying to draw a projectile motion graph using MATLAB script. But not getting the graph. Can anyone please check my code and tell me what is the mistake.

I don't know how to take θ positive and negative when above and below the horizontal. How can I write the code for it?

[alexderjuengere]

I don't have the Matlab Toolkit, so I can't run your code.

Maybe you have to convert from degree to radians before feeding it into the sinus or cosinus function?

I hastly translated your script in plain Labview G code, this is what I get:

[CanadaGuy]

You're on the right track. I made the changes directly in the MATLAB node and while not familiar with the expressions used, produces a reasonable trace.

With such simple functions, the Mathscript node (if available), or even the formula node could be used instead.

[jamiva · Accepted solution]

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This has nothing to do with LabVIEW, BUT...

If you shoot a projectile with a launch angle of 90deg (straight up in the air), it should come down on your head. Your result shows it landing quite a long distance away. So, I think your equation is wrong in the Matlab Script.

Got this equation from Wikipedia

Rearranging the terms to match your MathScript code, I get the following for "R":

R = d.*[sin(a)+A]

It's different than what you have. Try it and see if the results are more realistic.

[anny321dum]

Thank you for your reply. Do you think that it is something to do with the angle conversion from degree to radian?

[anny321dum]

Understood the mistake I have done. Thanks a ton.

[jamiva]

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@anny321dum wrote:

I don't know how to take θ positive and negative when above and below the horizontal. How can I write the code for it?

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This got me thinking a little more. The Wikipedia formula doesn't model the motion well for negative launch angles. Going back to the quadratic equation, there are actually 2 solutions for the range. You need to use the "plus" for positive angles and "minus" for negative angles.

Here is a quick VI implementing positive/negative launch angle

[jamiva]

I think it translates to your Matlab script as (please check my math):

R=d.*[sin(a)+A]   for theta>0
R=d.*[sin(a)-A]   for theta<0

and for special case of theta=0

R=v*sqrt(2*H/g)

[anny321dum]

Thank you very much for your reply. I got the correct vi.

[alexderjuengere]

I'm just curious:

have you translated the .vi from jamiva to the matlab node script language?

if yes, could you share this .vi?