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Homework Help: Electrons - Relativistic velocity addition

  1. Aug 6, 2012 #1
    electrons -- Relativistic velocity addition...

    1. The problem statement, all variables and given/known data

    an observer measures the velocity of two electrons, finding one with a speed c/2 in the x direction and the other c/2 in the y direction. what is the relative speed of the two electrons.

    2. Relevant equations

    3. The attempt at a solution

    Im not sure if this is right it seemed to easy.

    but suppose that electron 1 is called b and the other a

    then v(b)= √(c2/4+c2/4)
    since they are at right angles to each other. is this right?
  2. jcsd
  3. Aug 6, 2012 #2
    Re: electrons

    The velocities are very high, you need to use special relativity here.
  4. Aug 6, 2012 #3


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    Gold Member

    Re: electrons

    No. That is a non-relativistic velocity-addition and would give you the right answer for a speeding bullet on Earth but NOT for things traveling at relativistic speeds.

    Google relativistic velocity addition
  5. Aug 6, 2012 #4
    Re: electrons

    oh yeah that makes sense ok cool thanks.
  6. Aug 7, 2012 #5
    Re: electrons -- Relativistic velocity addition...

    How did you go with the rest of the assignment =P
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