Water polo’s eggbeater kick defies biomechanics, supercomputer says disposable masks are best – Physics World


Complex physics: a water polo goalkeeper uses the eggbeater kick to rise up in the water. (Courtesy: Ryanjo/CC BY-SA 3.0)

Water polo is a gruelling sport and even staying in one place requires the continuous effort of treading water. To extend their reach for the ball while stationary, players use a kick called the “eggbeater” to raise their upper bodies above the surface of the water. The kick is so called because the legs make large circles in the water.

Now Hideki Takagi of the University of Tsukuba’s swimming laboratory and colleagues have discovered that the efficacy of the eggbeater exceeds the predictions of conventional biomechanical theories based on Newton’s laws and hydrodynamics.

“Our study hints that water polo players are actually taking advantage of complex physics, including unstable vortices, to achieve this increased efficiency,” explains Takagi. The Japan-based team describes their surprising finding in Sports Biomechanics.

Mask calculations

What sort of mask is best for curbing the spread of Covid-10? Researchers in Japan have used the Fugaku supercomputer to compare the efficacy of disposable medical style masks with reusable masks made from woven fabrics – specifically cotton and polyester.

The calculations suggest that the disposable masks, which are made from a non-woven polypropylene fabric, stop more cough droplets that woven masks. The disposable masks are particularly good at stopping smaller droplets, while the woven masks are not – suggest the calculations.

Fugaku has recently earned the title of the world’s most powerful supercomputer and was also used to model the flow of droplets in an office and on a railway carriage. You can read more about the study in The Guardian.

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