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Special Relativity Spaceship Question

  1. Oct 5, 2014 #1
    1. The problem statement, all variables and given/known data
    bob and anna are in two space ships of proper length 100m; anna's ship passes bob's and is moving in the -x dir at v=0.75c. the front of anna's ship and the tail of bob's ship coincide at x=x'=t=t'=0. bob sits at the window in his ship and sees a clock inside anna's ship
    a) what position is the window in bob's space ship
    b) what time does this clock in anna's ship read

    2. Relevant equations
    x'=gamma(x-vt)
    x=gamma(x'+vt')
    t'=gamma(-v/c^2*x+t)
    t=gamma(v?c^2*x+t')
    delta t = gamma delta to
    L = Lo/gamma

    3. The attempt at a solution
    a)

    so if bob sees the clock at the end of anna's ship, then:

    L=Lo/gamma = sqrt(1-v^2/c^2)*Lo = sqrt(1-0.75^2)*(100)=66.1m <-- position of bob's window in his space ship (distance from the end of his spaceship to the window)

    b)

    i tried :

    x=100m
    v=0.75c

    t'=x'/v = 4.45 * 10^-7 s

    But I'm not sure if this is correct...
     
  2. jcsd
  3. Oct 5, 2014 #2
    One thing that isn't clear: Bob is situated at the front of his space ship?

    Chet
     
  4. Oct 5, 2014 #3
    The question doesn't state that. It's asking where the window is - I'm guessing that's the point at which he can see Anna's clock, and her window is at the end of her spaceship.
     
  5. Oct 6, 2014 #4
    So, under this interpretation, you are looking at the event at which x' = L0 and t = 0. In part a, you showed that ##x=L_0/\gamma##. Now all you need to do is substitute this into the equation for t'.

    Chet
     
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