1. Not finding help here? Sign up for a free 30min 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!

Air resistance - find Vx(t) and Vy(t)

  1. Sep 29, 2011 #1
    Suppose at time t= 0 the football is kicked with initial velocity components Vxo and Vyo. Solve the equations above to find Vx(t) and Vy(t). You can make use of the formulas we worked out in class.

    "Equations above":
    ax = -kvx
    ay = -g-kvy

    formula worked in class:

    v(t) = (g/k)(1-e^-k(t-to)) + Voe^-k(t-to)

    so...

    Vx(t) = Vocosθe^-kt

    Vy(t) = (9.8m/s^2/k)(1-e^-kt) + Vysinθe^-kt

    Is this correct?
     
  2. jcsd
  3. Sep 29, 2011 #2
    Next problem is to integrate that to get a formula for x(t) and y(t)

    Assuming the above is correct, here's what I got:

    x(t) = -V0sin[itex]\theta[/itex]e-k(t-to)/k +V0sin[itex]\theta[/itex]/k

    y(t) = -ge-k(t-t0)/k2 + V0cos[itex]\theta[/itex]e-k(t-t0) + g/k2 - V0cos[itex]\theta[/itex]/k
     
  4. Sep 29, 2011 #3
    Please help [URL]http://img.photobucket.com/albums/v253/Hatsuharu1399/gdkifmqq.gif[/URL]
     
    Last edited by a moderator: Apr 26, 2017
  5. Sep 29, 2011 #4
    Come on guys

    Let me rephrase my question

    How to I include air resistance (k) into a projectile motion problem?

    In this problem, k = 0.1/s

    so do I stick that into the acceleration equation to get a new acceleration?

    ax = -kVx
    ax = -0.1/s * Vx

    ay = g - kvy
    ay = -9.8m/s^1 - 0.1 * Vy

    This part seems okay, but what do I use for Vx and Vy? Is it the initial velocities???

    In this problem I was given Vx0 = 12 m/s and ax0 = 10 m/s

    So if I use that, I get these constant velocities

    ax = -1.2 m/s^2
    ay = -10.8 m/s^2
     
  6. Sep 29, 2011 #5

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

     
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Air resistance - find Vx(t) and Vy(t)
  1. Quick Vx and Vy prob (Replies: 2)

  2. V(t) and x(t) (Replies: 1)

Loading...