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Kinetic theory of gases momentum

  1. Oct 3, 2008 #1

    delta px = pf - pi
    mvf - mvi
    mvx - (-mvx) <<<<---- where does this second negative come from ? what am i missing here?

    in my book it shows that
    delta px = - mvx - (mvx) = -2mvx
  2. jcsd
  3. Oct 3, 2008 #2

    Doc Al

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    Staff: Mentor

    When a particle bounces elastically off a wall, its velocity (and momentum) changes direction. Does that help?
  4. Oct 3, 2008 #3
    yes i understand that so the second negative appears after the particle has hit the wall resulting in the 2mvx ?
  5. Oct 3, 2008 #4
    ok i got it mvi = -mvf therefore -mvi - mvf = -2mvx
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