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: How long does a moun live during a measurement

  1. Sep 5, 2012 #1
    1. The problem statement, all variables and given/known data
    A muon with a kinetic energy of 200 ± 0.05 MeV
    is produced in a linear accelerator. The rest
    mass of the muon is 106 MeV/c2.
    (a) Calculate the speed of the muon (in units of c),
    (b) Calculate the linear momentum (in units of eV/c),
    (c) How long does it live during the measurement?
    (d) Find the lifetime of the muon.
    (e) What is the distance traveled by muon in laboratory
    before it disappears (use c = 3 x 108 m/s)? Could
    this distance be measured?
    (f) For identifying a muon what method do you think
    that is better: (1) based on measurements of energy
    or (2) based on measurements of distance? Why?

    I am having trouble with part c

    2. Relevant equations
    (1 stands for naught)
    E = E1 + K
    deltaE dot deltaT = h (I dont understand this equation)
    deltaT = h/deltaE

    3. The attempt at a solution
    I found this and the solution online I understand part a and b then answers are respectivley v=.938c and p=287MeV/c. It is part c that im struggling with this is what my instructor does he says deltaE dot deltaT = h which isnt on my equation sheet so im not sure about this. Then he states E = K + E1 remains constant, then sets deltaE=deltaK = .1MeV I think I understand where he got the equality part and I think I get how he got .1 I assume he did this .05-(-.05) = .1 = deltaK = deltaE. But I am not sure as to why he did this. Then deltaT = h/deltaE = (6.58e-16 eV.s)/(1e5 eV) = 6.58e-21s. How the heck did he obtain 6.58e-16 I am confused?
  2. jcsd
  3. Sep 6, 2012 #2
    Ouch! no replies yet very weird I guess maybe I was confusing or something.
  4. Sep 6, 2012 #3
    The equation you don't understand seems to be the uncertainty principle for energy and time.
  5. Sep 6, 2012 #4
    lol after looking up the uncertainty principle I agree thats what it is but I really need to know where the .1 and 6.58e-16 came from?
  6. Sep 7, 2012 #5
    .1 comes from the uncertainty of energy. 6.58e-16 is Planck's constant in eV.s.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook