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Parametric plot / I just need to check my work (quick)

  • #1
372
0
[tex]x(t)= \left( u\cos A \right) t[/tex]

and

[tex]y(t)= \left( u\sin A \right) t - \frac{gt^2}{2} + h[/tex]

represent the horizontal and vertical coordinates of a batted or thrown baseball. [tex]A[/tex] is the initial angle of elevation and [tex]u[/tex] is the initial speed of the ball. I need to plot [tex]x(t)[/tex] and [tex]y(t)[/tex] parametrically. I'm given the following

[tex]u = 125 \mbox{ ft/s}[/tex]

[tex]g = 32 \mbox{ ft/s}^2[/tex]

[tex]h = 3 \mbox{ ft}[/tex]

[tex]A[/tex] may take several different values. Here follows the random choices I made and the corresponding graphs:

[tex]A=\frac{\pi}{3}[/tex]

http://img25.imagevenue.com/img.php?loc=loc93ℑ=663_parametricplot_1.jpg

[tex]A=\frac{4\pi}{9}[/tex]

http://img6.imagevenue.com/img.php?loc=loc123ℑ=26c_parametricplot_2.jpg

[tex]A=\frac{\pi}{2}[/tex]

http://img6.imagevenue.com/img.php?loc=loc123ℑ=26c_parametricplot_2.jpg

Could you please take a quick look at those graphs? In my opinion, there seems to be something wrong.

Thank you
 
Last edited:

Answers and Replies

  • #2
NateTG
Science Advisor
Homework Helper
2,450
5
I can't see the images. You should be getting parabolas for the first two, and a vertical line for the third (since the ball goes straight up and down.)
 
  • #3
372
0
NateTG said:
I can't see the images. You should be getting parabolas for the first two, and a vertical line for the third (since the ball goes straight up and down.)
Oh, I'm sorry about that. I actually tested the links, but a minute later they just wouldn't work. If you still wanna take a quick look, I placed them at:

photos.yahoo.com/thiago_j

They're the only ones there. What you said about the shapes sound right to me, but that's not what I have. They are pretty much the same. I used the command (mathematica 5):

ParametricPlot[{x(t), y(t)}, {t, t_min, t_max}]

Anyway, that's definitely stange.
 
  • #4
2,209
1
The discrepancy is probably because you cite g in feet per second squared and your initial velocity in meters per second. Your equation forms are correct.
 
  • #5
372
0
Oh, no!!! That's a typo. u = 125 ft/s. The units are incorrect in my 1st post.
 
  • #6
372
0
whozum said:
Your equation forms are correct.
I don't have a clue what else I could do.
 
  • #7
372
0
I managed to get in my calculator what NateTG predicted: "getting parabolas for the first two, and a vertical line for the third". All I gotta do now is go over my mathematica command so that I can fix it.

Thank you guys
 

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