1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Muons and Relativity

  1. Jan 25, 2015 #1
    1. The problem statement, all variables and given/known data
    A muon has a lifetime of 2.0x10^-6 seconds when at rest, after which time it decays into other particles
    a) Ignore any effects of relativity discussed in this section. If the muon was moving at 0.99c, how far would it travel before decaying into other particles, according to Newtonian mechanics?
    b) How long would the muon last, according to an observer in earths frame of reference?
    c)How far would the muon actually travel, when viewed moving at 0.99c?
    d) Compare the two distances travelled. Explain why this type of evidence is excellent support for the theory of relativity.

    2. Relevant equations

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

    3. The attempt at a solution

    a) (0.99)(3x10^8) = v
    v = 2.97x10^8

    d = (2.97x10^8)(2.2x19^-6)
    d = 653.4 m

    b) tm = ts/ (1-v^2/c^2)
    tm = 2.2x10^-6/0.141
    tm = 0.000015602 s

    c) d = vt
    = (2.97x19^-6)(1.56x10^-6)
    = 463.32 m

    d) ?
  2. jcsd
  3. Jan 25, 2015 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    What are you calculating in (b) ? The expression is not your relevant formula and the calculation is way off !
    Fix that and then c and d will be a lot more doable.
  4. Jan 26, 2015 #3


    User Avatar
    Education Advisor
    Gold Member

    Ok, couple typos there. You forgot the square-root sign. And it might be helpful if you converted your tm into scientific notation.

    The (2.97x19^-6) looks like you intended to write (2.97x10^8) but your fingers got away from you.
    Check the (1.56x10^-6) .
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted