일반물리학 2 — Relativity: Problem 51

51 The mean lifetime of stationary muons is measured to be \(2.2000\ \mu\text{s}\). The mean lifetime of high-speed muons in a burst of cosmic rays observed from Earth is measured to be \(20.000\ \mu\text{s}\). To five significant figures, what is the speed parameter \(\beta\) of these cosmic-ray muons relative to Earth?