Physics discovers the body best equipped for hula hoop

Jan. 3 () –

New York University Mathematicians They have explained for the first time the physics behind the hula hoopthe famous game that consists of spinning a hoop around the waist.

“What keeps a hula hoop held up against gravity?” and “Are some body types better at hula hooping than others?” The researchers explored and answered these questions with findings that also point to new ways to make better use of energy and improve robotic positioners.

“We were specifically interested in what types of movements and body shapes could successfully sustain the hula hoop and what physical requirements and restrictions are involved,” he explains. in a statement Leif Ristroph, associate professor at New York University’s Courant Institute for Mathematical Sciences and senior author of the paper, which appears in Proceedings of the National Academy of Sciences (PNAS).

To answer these questions, the researchers replicated, in miniature, a hula hoop at New York University’s Applied Mathematics Laboratory. In a series of experiments with hula hoop robotstested different shapes and movements, using 3D printed bodies of different shapes (e.g., cylinders, cones, hourglasses) to represent human shapes one-tenth the size. A motor made these shapes rotate, replicating the movements we make when hula hooping. Hoops approximately 15cm in diameter were dropped onto these bodies, and high-speed video captured the movements.

The results showed that The exact shape of the twisting motion or the shape of the body’s cross section (circle versus ellipse) was not a factor in the hula hoop.

“In all cases, good rotating movements of the hoop around the body could be created without any special effort,” explains Ristroph.

KEEPING THE HOOP ELEVATED REQUIRES A SPECIAL BODY TYPE

However, keeping the hula hoop elevated for a significant period of time was more difficult, since it required a special “body type”: one with a sloping surface like “hips” to provide the proper angle for pushing the hula hoop and a curved shape like “waist” to keep the hula hoop in place.

“People have many different body types: some have these slope and curvature traits in the hips and waist and some don’t,” Ristroph notes. “Our results could explain why some people are natural hula hoopers and others seem to have to try harder.

The authors of the article carried out mathematical models of these dynamics to derive formulas that explained the results, calculations that could be used for other purposes.

“We were surprised that an activity as popular, fun and healthy as hula hoop was not understood at even a basic physics level,” says Ristroph. “As we progress in the investigation, We realized that the mathematics and physics involved are very subtle, and the knowledge gained could be useful in inspiring engineering innovations, harvesting energy from vibrations, and improving robotic positioners and conveyors used in industrial processing and manufacturing.”