Ellastic collision w/rebound

  1. Jan 2, 2012 #1
    1. The problem statement, all variables and given/known data

    A 150 kg cart moving at 13 m/s east collided with a 420 kg wagon moving at 5.0 m/s east.
    The cart rebounded westward with a speed of 3.0 m/s . What was the speed of the wagon after the collision? Observe standard Cartesian coordinates.

    2. Relevant equations

    KE1+KE2=KE1'+KE2'
    conservation of momentum
    conservation of kinetic energy in elastic collisions


    3. The attempt at a solution
    (0.5)(150)(13)2+(0.5)(420)(5)2=(0.5)(150)(-3)2+(0.5)(420)v2
    v=9.0m/s

    Answer as given is 11m/s
     
    Last edited: Jan 2, 2012
  2. jcsd
  3. Jan 2, 2012 #2
    the problem itself doesn't say that the collision is elastic. so just use conservation of momentum here.
     
  4. Jan 2, 2012 #3
    issacnewton is right !!!
    Conservation of kinetic energy is valid only when coefficient of restitution(e) is 1
    here its not specified, so you must use momentum conservation.

    ALSO:
    if e is given and is ≠1 then you may use:
    (v2 - v1) = e(u1 - u2)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?