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Homework Help: Kinematics equations with collision fo 2 balls

  1. Oct 1, 2008 #1
    1. The problem statement, all variables and given/known data
    a ball is shot straight up from the ground with speed Vo. simultaneously, a second rubber ball at height h directly above the first ball is dropped from rest
    at what height above the ground do the balls collide?asnwer should be a symbolic expression in terms of Vo and g.

    2. Relevant equations
    kinematics equations

    3. The attempt at a solution
    we can use (delta)x = Vot + 1/2 a t2 and since we know that the final positions are equal we can write this equation for the 2 balls and make them equal to each other
    but the equation of the second ball would have a x(initial) for the ball in the equation (assuming the base line is the ground).........

    can someone help me out please. Thanks in advanced
  2. jcsd
  3. Oct 1, 2008 #2


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    Homework Helper

    You mostly have it.
    Construct the upward equation first:
    X=Vo*t - 1/2*g*t2

    Then construct the equation from rest:
    X= h - 1/2*g*t2

    If you solve for t then you just substitute into one of the x equations for the height.
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