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Time dialation

  1. May 23, 2010 #1
    An astronaut is travelling at a constant speed of 2.40x10^8 m/s relative to earth through space. according to timing devices aboard the space vehicle the trip took 1.25 years. how long did the trip last if measured relative to earth
    HELP PLEASE!!!!!!!
     
  2. jcsd
  3. May 23, 2010 #2
    I guess the answer is 2.08333 years.
    1.25=x{1-(v/c)^2}^.5
    x=2.08333
     
    Last edited: May 23, 2010
  4. May 23, 2010 #3
    thats right!!
    but how did you get that?
    do you need to convert the velocity?
     
  5. May 23, 2010 #4
    no you don't because , when we apply the formula (v/c)^2 both v and c are in same units i.e m/s...............
     
    Last edited: May 23, 2010
  6. May 23, 2010 #5
    hmm im still not getting the right answer when i plug it in to my calculater..
     
  7. May 23, 2010 #6

    DaveC426913

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    Gold Member

    Set the calculator aside, write it out on paper first.
     
  8. May 23, 2010 #7
    see the formula is t1 = t2 * { 1 - (v/c)^2 }^(1/2)
    where t1 is time in space shuttle (at 2.4...velocity)
    t2 is time measured on earth
    c is velocity of light
    v is velocity of space ship
    The above formula is time dilation formula .......
    now try it again

    ya you could do it on paper too, its easy calculation.........
     
    Last edited: May 23, 2010
  9. May 23, 2010 #8
    okay so it would be something like
    1.25/ (1-(2.4x10^8)2)^(.5)
    which gives me a negative square root
     
  10. May 23, 2010 #9
    The equation should be x= 1.25/{1-(v/c)^2}^(1/2) with (v/c) and not (c/v).

    Use v= 2.40x10^8 m/s and c= 2.99792458x10^8 m/s and you should get the right answer.
     
  11. May 23, 2010 #10
    dude it is not v^2 .....but......it is v^2/c^2.........
    where c=299792458 m/s and
    v is 2.4*10^8 m/s
     
    Last edited: May 23, 2010
  12. May 23, 2010 #11
    okay i got ittt finally
    thanks guyyys
     
  13. May 24, 2010 #12

    DaveC426913

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    Gold Member

    The lesson here, I hope you see, is that, if you rush through the work just to get an answer, you're not paying attention. Setting aside the calculator forces you to ensure that the process leading up to the number at the end is the important part.
     
  14. May 24, 2010 #13
    pmor@hotmail.
    I am sorry for that mistake i.e replacing c by v...........
     
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