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Homework Help: Percentage of kinetic energy after an elastic collision

  1. Mar 3, 2008 #1
    1. The problem statement, all variables and given/known data

    A stationary object with mass mb is struck head-on by an object with mass ma that is moving initially at speed v0.

    If the collision is elastic, what percentage of the original energy does each object have after the collision?

    KA2/K1 = ?

    KB2/K1 = ?

    2. Relevant equations

    K1 = 1/2mav1a^2 + 1/2mbv1b^2

    K2 = 1/2mav2a^2 + 1/2mbv2b^2

    3. The attempt at a solution

    K1/K2A = (1/2mav1a^2 + 1/2mbv1b^2)/(1/2mav2a^2)

    = v1a^2/v2a^2 + mbv1b^2/mav2a^2

    I'm not sure how to proceed from here and get a percentage.

    any help is appreciated.
  2. jcsd
  3. Mar 3, 2008 #2
    mbvo=mbv1+mav2(mv conserved)
    mbvo^2= mbv1^2+mav2^2(KE conserved)
    making use of these equations, find v1,v2 in terms of mass. and vo...
  4. Mar 3, 2008 #3
    v0 = v1 + mav2/mb

    v1 = v0 - mav2/mb

    v2 = mbv0/ma - mbv1/ma

    found the velocities, but I'm not sure how to proceed.
  5. Mar 3, 2008 #4

    I'm not sure what to do with these values?

    plug them into the kinetic energy equations and solve perhaps?
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