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 ts=? v=2.0x10^8 m/s tm=1.6x10^-8 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.