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How to figure out a equation given the variables

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data
    Starting from the constant-acceleration kinematic equations, write a formula that gives vf in terms of t, xi, xf, and a.



    2. Relevant equations



    3. The attempt at a solution
    I tried using vf = vi + at but it was incorrect. Is there another way where i can solve for vf using the 4 needed variable above? thanks
    Also I have tried using this : (xf-xi)+(1/2at) = vi then substitute vi with this equation vf = vi+at. After that I got (xf-xi)+at = vf but it was still incorrect.
     
    Last edited: Sep 8, 2009
  2. jcsd
  3. Sep 9, 2009 #2

    rl.bhat

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    (xf-xi)+(1/2at) = vi
    This equation is wrong.
    It should be
    (xf-xi)-(1/2at^2) = vi*t
    From the equation vf = vi + at find vi and put it in the above equation and rearrange to get vf
     
  4. Sep 9, 2009 #3
    what I got was ((xf-xi)-(1/2at^2)/t))+at = vf
     
  5. Sep 9, 2009 #4

    rl.bhat

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    vi*t = (vf - at)t = vf*t -a*t^2
     
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