The Newton's cradle is a device that demonstrates the conservation of momentum and the conservation of energy with swinging spheres. Wikipedia

A device that demonstrates conservation of momentum and energy via a series of swinging spheres Wikipedia Disambiguation

Device that demonstrates conservation of momentum and energy via a series of swinging spheres Wikidata

A device that demonstrates conservation of momentum and energy via a series of swinging spheres. When a sphere at one end is lifted and released, the resulting force travels through the line and pushes the opposite sphere upward, repeating the process as it swings back down. Wiktionary