The slinky is a toy I had as a youngster and remember to this day. It is a precompressed helical spring invented in 1943 by Richard T. James.
He was a Naval mechanical engineer stationed at William Cramp & Sons Shipyard when he accidentally knocked a spring off the table and it basically “walked” to the floor down a series of books and boxes and such. By 1945 he had them on demo at Gimbals in Philadelphia in November and sold all 400 units. The rules that govern the mechanics of a Slinky are Hooke’s Law and the effects of gravitation. Read more about Slinky’s at Wikipedia.