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Homework Help: Special Relativity

  1. Jun 15, 2011 #1
    A star is 40 light years from Earth.
    (a) How far would you measure this distance to be if you travelled it in a spaceship moving at 1.00X10^8 m/s

    (b) How long would the trip last (for you)?

    Can someone please help me out with this question and what equations I should use to solve this, thanks in advance
  2. jcsd
  3. Jun 15, 2011 #2


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    Gold Member

    Look up length contraction, this should be a fairly simple question.
  4. Jun 15, 2011 #3
    okay so for part a, convert light years into meters and that will be the rest length or the distance observed by someone from earth and then I need to solve for the relativistic length of the distance observed from someone in the spaceship?

    And then for part b, use the rest length I calculated in part a, and use the velocity equation v = d/t and solve for the time, which in this case would be the time it would take the space shuttle to reach the star observed by someone on earth and use that to find the time that the person in the space shuttle would experience?
  5. Jun 15, 2011 #4


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    Yes. It would be shorter, of course.

    Sure, but the more direct approach is using the contracted length from part a) and the fact that you know what speed the ship is traveling at, and immediately solve for the time you see as someone on the ship.
  6. Jun 15, 2011 #5
    Perfect, thanks for helping and explaining this rather than just giving me an answer.
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