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Homework Help: Momentum: Collision in two dimensions

  1. Oct 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Fast Eddie McSpeedy is a receiver for the Kennesaw Kilowatts in the Metro Metric Football League and Big Bobby Clobber plays defense in the rival Marietta Megatons. Eddie has a mass of 85 kg and Bobby has a mass of 140 kg. Eddie catches the ball and runs eastward at 2.4 m/s until he collides with Bobby. Bobby’s velocity is 1.2 m/s in a direction 30 degrees south of west until he collides with Eddie.
    (a) If Eddie and Bobby collide COMPLETELY INELASTICALLY what are each of their final velocities?
    (b) If the collision between the two players lasts 1.5 seconds, approximately how much force does each player experience during the collision?

    2. Relevant equations

    3. The attempt at a solution
    A. I have split the initial momentum up in the x and y directions for the players and put it in vector form. I am Not sure how to get the final momentum of the players when stuck together.
    B. All I have is the initial momentums. I do not know how to get the final momentum for the players if the collide 1.2 seconds. I think i need to find dP/dt in order to get the force exerted on each player.
  2. jcsd
  3. Oct 8, 2012 #2


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    Homework Helper

    hi lksmith17! :smile:
    the final momentum is the sum of the two initial momentums :wink:

    (and of course divide by the total mass to get the final velocity)
    force = rate of change of momentum = ∆P/∆t :smile:
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