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Homework Help: 3 boxcars moving along frictionless track hits a motionless boxcar

  1. Feb 20, 2012 #1
    1. The problem statement, all variables and given/known data
    Three boxcars are rolling along a virtually frictionless track at 20m/s when they strike another boxcar sitting motionless on the track. what is the new speed of the 4 coupled bovcars? all the boxcars have the same mass


    2. Relevant equations
    3rd or 2nd newton law


    3. The attempt at a solution
    m_a(20) + m_b(20) + m_c(20) + m_d(0) = m_a(v_f) + m_b(v_f) + m_c(v_f) + m_d(v_f)
    since all of the masses are equal i cross all of them out.
    60 = 4v_f
    v_f = 15m/s
     
    Last edited: Feb 20, 2012
  2. jcsd
  3. Feb 20, 2012 #2

    PeterO

    User Avatar
    Homework Helper

    That is the correct answer to the problem you described.
     
  4. Feb 20, 2012 #3
    thankyou.
     
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