Damn your yellow stick. Where are we going?


A Waboba is a ball that bounces on water (wa-ter bo-uncing ba-ll). That makes it kind of unusual since a simple experiment will show that many balls do not bounce on water. And that raises an interesting question–how does the Waboba work?

Today we get an answer from Michael Wright at Brigham Young University in Utah and a few buddies. These guys videoed the way three balls interact with water when bounced.

A Superball, which is solid and so has a relatively small surface area for its mass, burrows deep into the water, even when it hits at a shallow angle. So it does not bounce.

A raquet ball, on the other hand,is hollow and so has a larger surface area ratio to mass ratio. When thrown at a shallow angle, it penetrates only a small distance into the water creating a depression in the surface through which it planes back onto the surface. So it rebounds a little.

The Waboba is hollow but it is also soft. (…) Because it is soft, the ball flattens into disc-shape when it hits the surface and this allows it to aquaplane efficiently across the surface. (…)

Why might this be useful? Wright and co don’t say in their video but the fact that one of the team is with the Naval Undersea Warfare Center in Newport might offer a clue.

{ The Physics arXiv Blog | Continue reading }

artwork { Ellsworth Kelly, Yellow White, 1961 }