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!

Two Balls Colliding. Check my work please!

  1. Sep 24, 2010 #1
    [PLAIN]http://img178.imageshack.us/img178/4781/345b.jpg [Broken]

    So I said v=v0-gt, and at the highest point, v=0, so t=v0/g.
    I also said uy=u0sinx-gt, and ux=u0cosx.
    So at t=v0/g, both balls have to be at their highest pint, and when uy=0, t=u0sinx/g...so equating the two times, I find u0sinx=v0...which I guess is obvious without calculation.
    So uy0=v0, and ux0=v0cotx, and u0=v0/sinx.
    In this time, the left ball must travel d, so ux0*t=v0cotx*v0/g=v02cotx/g=d...
    I did some rearranging and found that v0=(d*g*tanx)1/2.
    Since u0=v0/sinx=(d*g*tanx)1/2/sinx, we need to minimize (tanx)1/2/sinx= (1/(sinxcosx))1/2...which is a minimum at x=45o, and when x=45o, v=(d*g)1/2.
    Is this right?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 24, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Looks right to me.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook