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Homework Help: Elastic Collision Problem

  1. Dec 14, 2008 #1
    Elastic Collision....Problem

    The problem states. The collison is elastic and head on. One ball has a mass of m1=.250kg and initial velocity of 5.00m/s. The other has a mass of m2=.800kg and is initially at rest. No external forces act on the ball. What are the velocities after collision.

    So far I got up to a certain point and I get stuck.

    I deduced that

    (Vf1)^2 = (Vo1)^2 - (M2/M1)(Vf2)^2
    Vf2 = (M1/M2)(Vo1-Vf1)

    Now when I substitute Vf2 into the first equation I get

    (Vf1)^2 = (Vo1)^2 - (M2/M1)[(M1/M2)(Vo1-Vf1)]^2

    This is where I get stuck. I can't solve for Vf1. I have the answer but I want to learn the steps to get to.

    Vf1= (M1-M2/M1+M2)Vo1

  2. jcsd
  3. Dec 14, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Elastic Collision....Problem

    Expand the right hand term, then rearrange so that you end up with a quadratic equation for Vf1.
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