Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook