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Homework Help: Elastic Collision of two blocks

  1. Dec 10, 2007 #1
    1. The problem statement, all variables and given/known data

    Block A of mass, mA = 2.0 kg, is moving on a frictionless surface with a velocity of 5.0 m/s to the right and another block B of mass, mB = 8.0 kg, is moving with a velocity of 3.0 m/s to the left, as shown in the diagram below. The two block eventually collide.

    a. If the collision is elastic, what are the final velocities of the two blocks?

    3. The attempt at a solution

    (2.0)(5.0) + (8.0)(-3.0) = (2.0)vaf + (8.0)vbf
    10 – 24 = (2.0)vaf + (8.0)vbf
    -14 = (2.0)vaf + (8.0)vbf divide the equation by 2
    -7 = vaf + 4.0vbf //equation 1
    So, I don't know now how to solve for these two final variables.
  2. jcsd
  3. Dec 10, 2007 #2
    you need to put also the kinetic energy conservation law.

    bye marco
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