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Special relativity of a rocket

  1. May 31, 2009 #1
    1)
    How fast must a rocket travel on a journey to and from a distant star so that the astronauts age 12.0 years while the Mission Control workers on earth age 130 years ? c


    2)
    As measured by Mission Control, how far away is the distant star? in light years


    my attempt
    1)
    Time in moving reference frame = (sqrt(1-beta))*time in inertial reference frame

    12/130 = sqrt(1-beta)
    12/130 ^2 = 1- beta
    12/130^2 = Tn
    tn = 1-beta
    beta = 1-td
    beta = v^2/c^2

    converting light years to seconds (1ly = 31556296 seconds)
    ((12*31556926) / (130*31556926))^2 = 8.520*10^-3
    1-(8.520*10^-3) = 0.99147 = beta
    v^2/c^2 = 0.99147
    sqrt(0.99147*c^2) = v
    v/c = 0.9957 c which is 0.9957 as a fraction of the speed of light that the rocket has to be traveling
    this was correct

    2)
    not quite sure how to solve the next one
     
  2. jcsd
  3. Jun 1, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Good. Note on terminology: Beta usually stands for v/c, not v^2/c^2.

    According to Mission Control, how fast was the rocket moving and how long did it take to reach its destination? (Use basic kinematics.)
     
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