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Homework Help: Double cheking momentum problem

  1. Apr 6, 2013 #1
    1. The problem statement, all variables and given/known data
    A bullet of mass 0.21 kg is fired from a gun of mass 5.6 kg. If the guns recoil speed is 2.5 m/s, what speed must the bullet have as it leaves the gun?

    2. Relevant equations

    m1V2 + m2v2ii = m1v1i + m2v2i
    m1 = gun, m2 = bullett
    3. The attempt at a solution

    The terms on the right side drop out.
    m1V2 + m2v2ii = m1v1i + m2v2i
    m1V2 + m2v2ii = 0
    m1V2 = -m2v2ii
    divide by m2
    m1V2/-m2 = v2ii

    (5.6 kg x 2.5 m/s) / (0.21 kg)
    Since it asks for speed 66.6 m/s
    Is this correct I don't have a solution guide thanks.
  2. jcsd
  3. Apr 6, 2013 #2
    yep yep
  4. Apr 6, 2013 #3
    thx dude
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