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Homework Help: A Twin Paradox Question, totally lost.

  1. Sep 11, 2012 #1
    1. The problem statement, all variables and given/known data

    Planet W is 12ly from earth. Anna and Bob are both 20 years old. Anna travels to planet W at 0.6c, quickly turns around, and returns to earth at 0.6c. How old will Anna and Bob be when Anna gets back?

    2. Relevant equations

    3. The attempt at a solution

    I've tried so many things and nothing is working. Apparently Bob is 60 years and Anna is 52 years. I'm completely lost on the idea of twin paradoxes, I could use some serious help. Thank you!
  2. jcsd
  3. Sep 11, 2012 #2
    Can you see why it is 60 years for Bob?

    For Anna, the distance to W and back is Lorentz-contracted.
  4. Sep 11, 2012 #3
    B/c 24cyrs/0.6c is equal to forty. Therefore you add them and get 60. Then, Anna is 52 years because the total distance that she appears to travel is 19.2? And 19.2cyrs/0.6c is equal to 32. add that to20 and you get 52. I ended up using length contraction. Sorry that was actually pretty easy!
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