The falling slinky

TL;DR

This paper analyzes the peculiar falling behavior of a slinky, comparing unphysical and physical models, revealing how wave propagation affects the motion of the bottom during free fall.

Contribution

It provides a detailed analysis of the falling slinky, including the effects of wave propagation and coil collisions, which were not thoroughly examined before.

Findings

The bottom of the slinky remains at rest until a wave reaches it.

Wave propagation speed significantly influences the timing of the bottom's motion.

Collision of coils creates a shock wave that alters the fall dynamics.

Abstract

The slinky, released from rest hanging under its own weight, falls in a peculiar manner. The bottom stays at rest until a wave hits it from above. Two cases -- one unphysical one where the slinky is able to pass through itself, and the other where the coils of the slinky collide creating a shock wave travelling down the slinky -- are analysed. In the former case, the bottom begins to move much later than in the latter.