Slinky

A helical spring toy that can walk down steps by transferring its shape and motion from one end to the other.

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Helical spring: A coil-shaped spring that stores and releases mechanical energy through changes in its length or shape. The Slinky’s coil geometry lets it stretch across a step and transfer motion between its ends.
Richard James: An American naval engineer who invented the Slinky in the early 1940s. James discovered the spring’s walking motion while developing devices to stabilize ship instruments.
Wave machine: A device that makes wave propagation visible through a linked series of moving elements. A stretched Slinky can act as a simple wave machine for pulses and reflections.
Slinky Dog: A pull toy with a Slinky spring forming its body between a dog’s head and tail. It adapts the spring into a character and walking toy rather than a stair-descending coil.
Elastic potential energy: Stored energy associated with the deformation of an elastic object. Stretching the Slinky stores energy that helps pull its trailing end forward.
Betty James: An American businesswoman who helped establish and lead the Slinky company for decades. Betty James named the toy and sustained its production and promotion after Richard left the business.
Longitudinal wave demonstration: An experiment that displays compressions and rarefactions moving through a medium. Compressing and releasing the Slinky makes a longitudinal pulse visible.
Hoberman sphere: An expanding geometric structure made from linked scissor-like struts. Unlike the Slinky’s continuous coil, it expands through articulated linkages.
Longitudinal wave: A wave in which disturbances move parallel to the direction of propagation. Compression and extension travel along the spring as one end moves toward the next step.
Slinky (brand): An American toy brand best known for its helical spring toy. The original spring toy became the defining product of a lasting brand.