Solving the paradox of the folded falling chain by considering horizontal kinetic energy and link geometry

TL;DR

This paper resolves longstanding paradoxes in the dynamics of a falling folded chain by incorporating horizontal kinetic energy and link geometry, leading to analytical solutions that match experimental and simulation data.

Contribution

It introduces a new analytical framework considering horizontal kinetic energy and link geometry to accurately predict tension and falling time of a folded chain.

Findings

Analytical solutions match experimental data.

Maximal tension is finite and predictable.

Total falling time depends on link geometry.

Abstract

A folded chain, with one end fixed at the ceiling and the other end released from the same elevation, is commonly modeled as an energy-conserving system in one-dimension. However, the analytical paradigms in previous literature is unsatisfying: The theoretical prediction of the tension at the fixed end becomes infinitely large when the free end reaches the bottom, contradicting to the experimental observations. Furthermore, the dependence of the total falling time on the link number demonstrated in numerical simulations is still unexplained. Here, considering the horizontal kinetic energy and the geometry of each link, we derived analytical solutions of the maximal tension as well as the total falling time, in agreement with simulation results and experimental data reported in previous studies. This theoretical perspective shows a simple representation of the complicated two-dimensional falling chain system and, in particular, specifies the signature of the chain properties.