# Homework Help: Relativity problem involving a muon

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1. Oct 15, 2014

### pstir2

1. The problem statement, all variables and given/known data
A muon is a subatomic particle with an average lifetime of 2.2 microseconds when stationary. In a burst of cosmic rays in the upper atmosphere, muons are observed to have a lifetime of 16 microseconds. What speed are they travelling at to achieve this?

2. Relevant equations
Time Dilation, Length Dilation, Mass Dilation, along with a few astrophysics formulas

3. The attempt at a solution
So I'm thinking this is relativity.
I used the time dilation formula:
tv=t0/Sqrt[1-(v2/c2)]

and worked out the velocity to be 2.972 x 108 m/s

My maths is fine (it doesn't need checking but check it if you want to). What I really need to know is if this is the correct process?

2. Oct 16, 2014

### Staff: Mentor

Yes, that's the right formula to be using.

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