“…It was realized in [38] that conservation of energy actually requires that τ + equals the tension, τ − , acting at the bight on the resting arm. As also pointed out in [44,45], different constitutive choices for these tensions would grant a full host of evolutions for the folded chain, including the one where the free arm falls freely [46]. The problem, however, is that we are not at liberty of choosing constitutive laws for τ + and τ − , at least as long as we model chains as inextensible strings, for which the tension in an internal reactive force to be determined.…”