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Homework Help: Special Relativity

  1. Mar 20, 2010 #1
    1. The problem statement, all variables and given/known data

    Consider two events
    [tex]ct_{1}\; =\; 3\; m,\; x_{1}\; =\; 2\; m,\; ct_{2}\; =\; 5\; m,\; x_{2}\; =\; 6m[/tex]

    1. What is the time difference between the two events?
    2. Find a reference frame for which the time difference is the negative of the time difference in the original frame.
    3. Calculate the invariant interval [tex]\left( \Delta s \right)^{2}=+c^{2}\left( t_{2}-t_{1} \right)^{2}-\left( x_{2}-x_{1} \right)^{2}-\left( y_{2}-y_{1} \right)^{2}-\left( z_{2}-z_{1} \right)^{2}[/tex] in both frames.

    2. Relevant equations

    3. The attempt at a solution

    I honestly don't have any idea what the first question is actually asking. How can I calculate a time difference when I am only given these distance figures with no velocities? It seems like an extremely poorly worded question.
    Last edited: Mar 20, 2010
  2. jcsd
  3. Mar 20, 2010 #2


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    The first question is just a unit conversion. What does c stand for?
  4. Mar 20, 2010 #3
    Well c = 3*108 ms-1. So t1 = 1*10-8 s and t2 = (5/3)*10-8 s.

    I guess assuming these are both observed from a laboratory frame of reference then the time difference is just t2 - t1 = (2/3)*10-8 s?

    It was a simple question, but the obscure way in which it was asked threw me off. Typical me, struggling with the simple stuff but I can much more easily understand the complicated things :smile: Thank you for your help. Hopefully I can do the other two problems myself!
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