Compression Wave

While the slinky is extended, the force of gravity displaces the slinky from its equilibrium by an amount equal to -kx, which is obtained from Hooke’s Law. The mass of the hanging portion of the slinky is dependent upon the length suspended, resulting in a larger displacement per coil closer to the point of suspension. As coils are released from the suspended point, the tension of the most extended portion of the slinky at the point of release pulls the coils downward. The released coils extend to compensate for the mass of the length of slinky below.

This compression and extension form a compression wave that travels down the slinky, changing the gravitational potential energy and spring potential energy of the slinky into kinetic energy.

If the bottom of the slinky is resting on a surface, some of the energy of the wave is reflected back up the slinky and continues to bounce until it dissipates. If the bottom of the slinky is hanging freely, the kinetic energy of the compression wave transfers to spring potential energy as the slinky extends further downward. The spring potential energy is then converted back into kinetic energy as the slinky bounces upwards. The slinky continues to bounce until the remaining energy has been dissipated to other objects or into unusable forms.

Licensed under the MIT open source license.