일반물리학 1 — Waves-II: Problem 67

67 If the form of a sound wave traveling through air is \(s(x, t) = (6.0 \text{ nm}) \cos(kx + (3000 \text{ rad/s})t + \phi)\), how much time does any given air molecule along the path take to move between displacements \(s = +4.0 \text{ nm}\) and \(s = -4.0 \text{ nm}\)?