Initial tension of the chain. Previous to its release, the chain, which is hanging from
its upper end, is subjected to a tension Γ as a consequence of its own weight. Mechanical
equilibrium imposes Γ(s) = μg(L+s), where s denotes the position in a frame of coordinates
attached to the chain, oriented upward; the origin is attached to the uppermost link. When
the chain is released, a longitudinal wave propagates from top to bottom, accelerating the
links downward.