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Homework Help: Momentem need equation help

  1. Jan 12, 2010 #1
    1. The problem statement, all variables and given/known data

    A 6500 kg freight car traveling at 2.5 m/s collides with an 8000 kg stationary freight car if they interlock upon collision find thier velocity

    2. Relevant equations

    M1 = 6500
    M2 = 8000 kg
    V1 = 2.5 m/s
    V2= ?

    i think the equation is p before = p after but im confused how i can use it

    3. The attempt at a solution

    not sure how to use the equation
     
  2. jcsd
  3. Jan 12, 2010 #2

    rock.freak667

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    Homework Helper

    Linear Momentum is mass x velocity. So before collision, what is the total momentum? After collision, the cars lock together, so what is the new mass and hence the final momentum?
     
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