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Lorentz Transformation

  1. Feb 27, 2017 #1
    1. The problem statement, all variables and given/known data
    Reference frame S' moves at speed v=0.94c in the +x direction with respect to reference frame S. The origins of S and S' overlap at t=t′=0. An object is stationary in S' at position x′ = 140 m .

    Part B
    What is the position of the object in S when the clock in S reads 1.3 μs according to the Lorentz transformation equations?

    2. Relevant equations

    3. The attempt at a solution
    I got part A, the Galilean transformation, easily enough. That came out to be 506.6 m. I've been getting the Lorentz transformation wrong and am thinking I'm missing something simple.

    I used γ=1/√(1-v^2/c^2) and obtained γ=2.93. I then multiplied this by the Galilean transformation and got ~1485, but Mastering Physics is saying no.
  2. jcsd
  3. Feb 27, 2017 #2


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    Gold Member

    HI Blue Kangaroo and welcome to PF

    You are missing a relevant equation involving the time transformation.

    You just can't multiply γ "by the Galilean transformation" (whatever that means) and expect to get a sensible answer.
  4. Feb 27, 2017 #3
    My line of thinking was since part A asked for the Galilean transformation (given by x=x'+vt') that that would go directly into the x=γ(x'+vt') equation.

    So do I then need to use t=γ(t'+vx'/c^2) and then plug that t into x=γ(x'+vt') to get my final answer?
  5. Feb 27, 2017 #4


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    Yes, you will get a system of two equations and two unknowns, the position in S that the problem asks you to find and time t' that the problem doesn't ask you to find.
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