College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 24

The muon is an unstable particle that spontaneously decays into an electron and two neutrinos. In a reference frame in which the muons are stationary, if the number of muons at t = 0 is N 0 , the number at time t is given by , where is the mean lifetime, equal to 2.2 ms. Suppose the muons move at a speed of 0.95 c and there are 5.0 × 10 4 muons at t = 0. (a) What is the observed lifetime of the muons (b) How many muons remain after traveling a distance of 3.0 km