The Newton's cradle is a device that demonstrates the conservation of momentum and the conservation of energy with swinging spheres. When one sphere at the end is lifted and released, it strikes the stationary spheres, transmitting a force through the stationary spheres that pushes the last sphere upward. The last sphere swings back and strikes the nearly stationary spheres, repeating the effect in the opposite direction. Despite its seemingly simple design, the Newton's cradle and its swinging, clicking balls isn't just an ordinary desk toy. It is, in fact, an elegant demonstration of some of the most fundamental laws of physics and mechanics. The toy illustrates the three main physics principles at work: conservation of energy, conservation of momentum and friction.

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