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Homework Help: Relativity: Spaceship travel times and distances

  1. Feb 12, 2017 #1
    1. The problem statement, all variables and given/known data
    A star is 95.0 year lights away from Earth. How much time does it take to a cosmic ship, which moves with speed 0.96 c, to reach the star, if it is measured from a watcher from a) Earth a)ship c)What si the distance of trip, based on the viewer from the ship?

    2. Relevant equations

    3. The attempt at a solution
    a) t=L/v=99 years
    c) Lr=L*sqrt(1-v^2/c^2)=26.6 years
    b) tr=Lr/v=27.7 years.
    I'm not sure if for this I should use tr=t/sqrt(1-v^2/c^2). Which one is the best to use because the results are different. But if I use tr=t*sqrt(1-v^2/c^2) it has the exact same result. If 27.7 years is the correct answer, then why should the length contract and time not dilate?
    Last edited: Feb 12, 2017
  2. jcsd
  3. Feb 12, 2017 #2


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    Is your problem description complete ?
    In part a) , what do you use for L and what do you use for v to get 99 y ?
  4. Feb 12, 2017 #3
    I had forgotten to put the speed. it is 0.96 c
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