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Homework Help: Deriving Equations

  1. Nov 11, 2008 #1
    HI I need help with the steps in between???? Im totally confused...

    So, how to derive the final equation from equation 1 and 2

    m1v1i+m2v2i=m1v1+m2v2f (Equation 1)

    1/2m1V1i^2+1/2m2v2i^2=1/2m1v1f^2+1/2m2v2f^2 (Equation 2)

    v1i-v2i= -(V1f-v2f) ( Final Equation)
  2. jcsd
  3. Nov 12, 2008 #2
    ok it does work out just abit of algebra

    First off what i did was rearrange your 2nd equation in terms of m1

    Substitute m1 into your first equation and simplify down

    you will end up with something like v1f(v2f^2-v2i^2)+v2i(v1i^2-v1f^2)=something

    now you have to realize that (v2f^2 - v2i^2) = (v2f - v2i)(v2f + v2i)

    More simplification from there and than you are done

    (Tip don't expand all the brackets out it will drive you nuts, rather cancel them down after recognizing that "now you have to realize that (v2f^2 - v2i^2) = (v2f - v2i)(v2f + v2i)"

    Thus from that you should get what are looking for

    Cheers Trent
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