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Deriving the head-on collision equation in terms of v2' and v1'

  1. Mar 9, 2008 #1
    [SOLVED] Deriving the head-on collision equation in terms of v2' and v1'

    I think I'm having an algebra issue here, but how is the momentum equation (where v2=0):

    m1(v1-v1')=m2v2'

    combined with v1+v1'=v2'

    to give:

    v2' = v1 [ 2m1/(m1+m2)]

    and

    v1' = v1 [(m1-m2)/(m1+m2)]


    I'm realizing this must be an elementary question since my book doesn't actually show how they derive those equations, but I'm not seeing it.

    Help someone?
     
  2. jcsd
  3. Mar 9, 2008 #2

    Tom Mattson

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    Plug v2'=v1+v1' into the first equation, and then solve for v1'.
     
  4. Mar 9, 2008 #3

    Hurkyl

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    So... you have two equations... and you are trying to eliminate one of the variables?
     
  5. Mar 9, 2008 #4
    Ok, I can find v1', but I'm confused on which equation to plug in where to get v2'.
     
  6. Mar 9, 2008 #5

    Tom Mattson

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    They gave you v2' in terms of v1 and v1', did they not?
     
  7. Mar 9, 2008 #6

    Hurkyl

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    There aren't very many options... why not try them all?
     
  8. Mar 9, 2008 #7
    Ok, feel dumb now. But since I'm exposed I may as well ask all my other dumb questions. Thanks for the help. :)
     
  9. Mar 9, 2008 #8

    Tom Mattson

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    Hey louise, you got it, so you should feel smart. :approve:
     
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