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Lorentz Velocity Transformations Question

  1. Sep 30, 2012 #1
    1. The problem statement, all variables and given/known data

    An electron and a positron are observed from the lab to move in opposite
    directions with a speed of 0.5c and 0.7c, respectively. Find the speed of the
    positron when observed in the electron's rest frame.


    2. Relevant equations
    in attached PDF


    3. The attempt at a solution
    in attached PDF
    ---------------------%------------------
    I would like you to check my solution, if it is wrong, show me where i went wrong, and give me a hint, if it's right, gimme a cookie!
    this forum has been helping me immensely with Modern Physics.

    Please refer to the attached Document
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Oct 1, 2012 #2
    You ended up deriving the velocity addition formula. I wonder why you could not just have used it directly. The result seems correct.
     
  4. Oct 1, 2012 #3
    if i don't derive it a couple of times myself, i won't memorize it, and i won't know "what" it means, ...
    i was taught physics 1 by a great professor who didn't use except two formulas (f=ma, and a=+- 9.8) we had to derive everything else..
    i remember he said once when we told him it was hard to derive the displacement from the acceleration... he looked at us with such a stare and said "Wow... are you all really that stupid! It's not that hard"...
     
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