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Homework Help: Momentum and Impulse. find final velocity!

  1. Jan 9, 2010 #1
    1. The problem statement, all variables and given/known data
    A 0.10-kg object moving initially with a velocity of 0.20 m/s eastward makes an elastic head-on collision with a 0.15-kg object initially at rest. What is the final velocity of the .10 kg object after the collision ?

    2. Relevant equations

    im not sure which equation to use :/

    3. The attempt at a solution

    i tried using m1v1+m2v2=(m1+m2) V
    but it didnt come out right.

    and i know the answer is -0.045 m/s
  2. jcsd
  3. Jan 9, 2010 #2


    User Avatar
    Homework Helper

    Hi maxjohnfresh, welcome to PF.
    i tried using m1v1+m2v2=(m1+m2) V
    This formula is true if both objects move together after collision.
    So use the formula
    m1v1i+m2v2i=(m1v1f+m2v2f) .
    Apply the conservation of energy and solve for v1f and v2f.
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