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Magnitude of a velocity vector with special relativity

  1. Mar 11, 2012 #1

    I'm trying to get my head around how velocity vectors work in special relativity. For example, in classical mechanics, the magnitude of the velocity would be given by:

    [tex]v^2 = \sqrt{v_x^2 + v_y^2 + v_z^2}[/tex]

    where [itex]v_x[/itex], [itex]v_y[/itex] and [itex]v_z[/itex] are the [itex]x[/itex], [itex]y[/itex] and [itex]z[/itex] components of the velocity respectively.

    What is the equivalent formula for use in special relativity. For example, if you knew the magnitude of the velocity, [itex]v[/itex] and the [itex]x[/itex] component of the velocity, what formula would you use to work out the [itex]y[/itex] component?

    With very many thanks,

  2. jcsd
  3. Mar 11, 2012 #2


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    Hi Froskoy! :wink:
    same formula! :smile:

    the special relativity rule for adding relative velocities has nothing to do with "de-componenting" a single velocity :wink:
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