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Length Contraction

  1. Jul 19, 2012 #1
    1. The problem statement, all variables and given/known data

    A spaceship moves past you at speed v. You measure the ship to be 300 m long, whereas an astronaut on the ship measures a length of 356 m. Find v.

    2. Relevant equations

    L=L1sqrt(1-v^2/c^2)

    3. The attempt at a solution

    I have tried this by using the above formula. I plugged in 300 for L and 356 for L1 and I have tried it the other way as well where I plug in 300 for L1 and 356 for L. The answer is in terms of c. I only have one try left and dont understand what Im doing wrong.
     
  2. jcsd
  3. Jul 19, 2012 #2

    TSny

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    You are looking for v in terms of c, which means that you are trying to find v/c. So, let x = v/c and write your equation as L = L1sqrt(1-x^2). Show us some of the details of how you would solve this for x.
     
  4. Jul 19, 2012 #3
    L/L1=sqrt(1-x^2)
    (L/L1)^2=1-x^2
    1-(L/L1)^2=x^2
    x=sqrt(1-(L/L1)^2)
     
  5. Jul 19, 2012 #4

    TSny

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    Good. That should you get you the correct answer.
     
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