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Relative length and velocities using Lorentz transformations

  1. Oct 27, 2011 #1
    1. The problem statement, all variables and given/known data
    Space ships A and B, each having a proper length of 100m, pass each other moving in opposite directions. According to the clocks on ship A, the front end of B takes 1.5 x 10^(-6) s to pass the entire length of A.

    a) what is the relative velocity of the two ships?

    b) according to clocks on ship B, how long does it take for the front end of A to pass the entire length of ship B?

    c) according to clocks on ship B, how much time passes between the time when the front end of A passes the front end of B and the time when the rear end of A passes the front end of B? Does this time interval agree with your answer to B? Should it?


    2. Relevant equations
    Lorentz matrices.


    ATTEMPTS:

    So here's whats confusing me: I want to apply the lorentz transformation of velocity addition to find the relative velocity of the spaceships, however I'm not sure how to do that since I don't know their respective velocities to begin with. Is there some way to derive the velocity of one or both of the ships given the time it takes for the front end of ship A to pass through the length of ship B? I wanted to simply take delta(x)/delta(t), but I dont know what to use for delta(x) since the problem only gives me the proper length and no velocity to apply a lorentz contraction. So any help with any part of this problem would be greatly appreciated!
     
  2. jcsd
  3. Oct 28, 2011 #2

    vela

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    What's the length of ship A in ship A's frame? That's the distance the front end of B travels in the 1.5 μs.
     
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