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Homework Help: Collision Problem

  1. Feb 25, 2004 #1
    A 1300kg car A stikes a parked 1200kg car B. Car B slides 2m after impact. The coefficient of friction between B's tires and the road is u=0.8. The coefficient of restitution is e=0.4. What is the velocity of A just before impact?

    I have the equations:

    mA*vA + mB*vB = mAvA' + mBvB'

    e = (vB' - vA')/(vA - vB)

    The initial velocity for B is zero so I still have three variables and only two equations. What other equation do I need to solve this problem? I thought about conservation of energy, but how does friction play into this?
  2. jcsd
  3. Feb 25, 2004 #2
    Energy is clearly not conserved, as the collision is clearly not elastic.

    The fact that Car B slid 2m after impact will give you the velocity of car B after the collision.

    Answer this question: How much velocity must a 1200kg car with a coefficient of kinetic friction of .8 have if it slides 2m before stopping?

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