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Homework Help: Relative time space travel

  1. Dec 9, 2011 #1
    1. The problem statement, all variables and given/known data
    I have a twin brother, and we're 30 years old. If i travel for three years at 2.55 X 10^8m/s (0.85c) while my brother is a rest on Earth, how much older than me will my brother be upon my return?


    2. Relevant equations

    t=To/√1-v^2/c^2

    3. Try to work out
    To=3
    T=?
    V= 2.55 X 10^8 m/s
    C= (.85c) 2.55 X 10^8 m/s
    T= 3/ (all of this under a square root sign -->)1-(2.55 x 10^8)^2/(2.55 x 10^8)^2
    t=3/0
    *i get stuck here because you cant have a zero in the denominator*
     
    Last edited: Dec 9, 2011
  2. jcsd
  3. Dec 9, 2011 #2

    BruceW

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    Homework Helper

    Hmm, you've done:
    [tex]T= \frac{3}{\sqrt{1- \frac{v^2}{v^2}}}[/tex]
    I'm guessing you've accidentally done this?
     
  4. Dec 9, 2011 #3
    Yes i used that equation, should I have used something different? If so what?
     
  5. Dec 9, 2011 #4

    BruceW

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    Homework Helper

    This was the right one, i.e. :
    [tex]\frac{3}{\sqrt{1- \frac{v^2}{c^2}}}[/tex]
    c is the speed of light, but you used v instead, which is why the denominator came out as zero.
     
    Last edited: Dec 9, 2011
  6. Dec 9, 2011 #5
    C = 3 x 10^8 m/s.
    Remember this: the difference in ages will be the difference in the proper time and dilated time.
     
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