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Homework Help: Elastic/completely inelastic collision

  1. Aug 9, 2010 #1
    1. The problem statement, all variables and given/known data
    Particle 1 of mass 230 g and speed 2.80 m/s undergoes a one-dimensional collision with stationary particle 2 of mass 400 g.

    2. Relevant equations
    What is the magnitude of the impulse on particle 1 if the collision is elastic?
    What is the magnitude of the impulse on particle 1 if the collision is completely inelastic?

    3. The attempt at a solution

    For the 1st Question, i found final velocity for particle 1, so that I can subtract the given initial velocity for particle 1 to get the impulse. i used this equation: v'1 = v1 (m1 - m2) / (m1 + m2), noting that initial velocity for particle 2 is zero ( as given ) and then I plugged in numbers and got -.755555
    Then I went back to equation for change in momentum: m1v'1 - m1v1 and got -817.7778 however this is wrong.

    for the 2nd Question
    I used: m1v1 + m2v2 = m1v'1 + m2v'2 , noting that m2v2 is zero ( as given v2 is zero ) and the m1v'1 = m2v'2 because they has to move together since they stick together. but Now i have two unknowns ( v'1 and v'2 ) and only 1 equation. I don't know how to solve it?

    m1: mass for particle 1
    m2: mass for particle 2
    v1: initial velocity for particle 1
    v2: initial velocity for particle 2
    v'1: final velocity for particle 1
    v'2: final velocity for particle 2

    Thank you.
  2. jcsd
  3. Aug 9, 2010 #2


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    Gold Member

    If they stick together, they will have a common final velocity.
    Last edited: Aug 9, 2010
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