The inertia of the rope depends on its \(\textit{mass per unit length}\) or \(\textbf{linear mass density}\) (SI units kg/m), which we denote by the Greek letter \(\mu\) (“mu”). If the rope is uniform, \(\mu\) is just equal to the mass of the rope divided by its length. A thick rope has more mass per unit length than does a piece of ordinary string and so has more inertia. As the mass per unit length of a rope increases, the wave propagation speed decreases.
If we take both restoring force and inertia into account, we find that the propagation speed \(v_{\mathrm{p}}\) of a transverse wave on a rope is