Why does the bottom of a falling Slinky stay at rest?

In this paper, we analyze the motion of a falling Slinky, starting from rest and initially suspended from one of its ends. It is well-known that under these conditions, the Slinky moves in an unusual way: its lower end remains at rest until the upper end collides with it – as if gravity were being challenged! We conducted a literature review and identified that the most widely disseminated explanation for this levitation phenomenon of the Slinky’s base during the Slinky’s fall relies on the concept of information (and does not seem to please many). We show that such a phenomenon can be explained – and reproduced through a computer simulation using a simple model – without the notion that “there is a finite time for the information that the Slinky was released at its top to reach its bottom”.

Keywords:
Falling Slinky; modeling; computer simulation