As any high-schooler will attest, there is no shortage of ways to demonstrate the frustrating complexities of physics. But one problem stands out as a favorite for showcasing physics' counterintuities -- the two-ball bounce problem.

The problem is demonstrated by dropping a smaller ball and larger ball together, the smaller ball positioned directly on top of the larger ball. The result -- using a tennis ball and basketball, for example -- is a smaller ball bouncing unexpectedly high, three or four times the height from which it was dropped.

Researchers at the University of Bristol recently revisited the classic classroom demonstration and located flaws in the traditional explanation.

Textbooks explain the phenomenon as a demonstration of two basic physic premises, Newton's law of restitution and the the law of conservation of momentum. It turns out, the explanation is based on a flawed reality.

The high bounce is the product of human error, as demonstrators aren't able to drop the balls simultaneously. Inevitably, the smaller ball is dropped a brief moment later, and it is this gap that enables the high bounce.

When Bristol researchers revisited the phenomenon using the preciseness of computers and the keen eye of a high-speed camera, they found the closer the balls are together when dropped, the less impressive the bounce.

That traditional explanation assumes two separate but simultaneous collisions -- the basketball bounces of the floor, the tennis ball bounces off the rebounding basketball. But unless the two balls are dropped with a sizable gap between them, the basketball is still in contact with the ground when the tennis ball hits -- the order of collisions is actually reversed.

What researchers determined, was that the basketball acts like a trampoline. Upon impact, the basketball's compression excites an elastic wave that catapults the tennis ball back into the air. The effect is weakened as the gap between the two dropped balls narrows.

"Understanding how spherical bodies behave when they collide has important implications when modelling 'granular materials', such as sand, as these are can be treated as a collection of lots of tiny spheres," Yani Berdeni, a PhD student in Bristol's engineering department, explained in a press release.

Berdeni and his colleagues published their findings in the Proceedings of the Royal Society A.