1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

  1. Jun 10, 2005 #1
    [tex]x(t)= \left( u\cos A \right) t[/tex]


    [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:







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

    Thank you
    Last edited: Jun 10, 2005
  2. jcsd
  3. Jun 10, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    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.)
  4. Jun 10, 2005 #3
    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:


    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.
  5. Jun 10, 2005 #4
    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.
  6. Jun 10, 2005 #5
    Oh, no!!! That's a typo. u = 125 ft/s. The units are incorrect in my 1st post.
  7. Jun 10, 2005 #6
    I don't have a clue what else I could do.
  8. Jun 10, 2005 #7
    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook