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Homework Help: Time Dialation

  1. Sep 11, 2006 #1
    Heres the question before I say anything else

    A beam of unknown elementary particles travels at a speed of 2.0 x 10^6 m/s. Their average lifetime in th ebeam is measrured to be 1.6 x 10^-8 s. Caclulate their average lifetime when at rest.

    hmm I have no examples to go by. I figure I will have to use the formula

    tm = ts/[sqrt(1-v^2/c^2)]

    where tm is the time it takes when the object is moving (for example when viewing from earth and ts is the stationary time, v is speed of the object and c is speed of light)

    I tried to do this by plugging in the numbers as

    v=2.0x10^8 m/s

    I didn't get the right answer of 1.2 x 10^-8 s so I am assuming im wrong.
    How do I do this correctly.
  2. jcsd
  3. Sep 11, 2006 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Well you are using the right formula and I get the right answer when I plug the numbers in. If you tell us what answer you get perhaps we can tell you what you're doing wrong.

    EDIT: just noticed you cited
    as what you've input.

    That could be the problem.
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