AssetID: 54826175
Headline: RAW VIDEO: Defying Gravity: Physicists Achieve "Impossible" Feat Of Rolling A Ball Vertically Down A Wall
Caption: A team of physicists from the University of Waterloo have achieved what was once thought impossible: a ball rolling vertically down a wall, defying the constraints of gravity. The breakthrough marks a significant challenge to conventional physics, where vertical rolling was believed to be unattainable. In their newly published paper, the team explains how they managed to make a sphere roll, rather than fall or slide, down a vertical surface - a phenomenon considered impossible under normal conditions. "On perfectly vertical surfaces, rolling is conventionally deemed impossible without external torque. While various species like geckos and spiders exhibit vertical locomotion, they cannot achieve rolling; instead, they fall," the researchers note. The team revisited basic principles from physics textbooks to explore the situation. They highlight how a rigid glass sphere of mass "m" behaves on an inclined plane of a similar rigid material, rolling freely down the plane under gravity when the angle of inclination is between 0° and 90°. But what happens when the surface becomes perfectly vertical, they ask? The intuitive response is that the sphere will simply fall, without making contact with the surface unless it has some initial roll. This is because, on a smooth vertical surface, the normal force (the force at the point of contact) is zero, and there is no static friction to generate the necessary torque for rolling. On sloped surfaces, the friction between the sphere and surface provides the torque required for rolling. However, on smooth vertical surfaces, friction is absent, making rolling impossible. Even with adhesive or sticky spheres, the ball would either stick or slide down the surface, rather than rolling. After months of theoretical calculations and a series of experiments, the Waterloo team found the key to unlocking this "impossible" feat. By carefully balancing the elasticity and softness of both the sphere and surface, they were able to create conditions where rolling could occur. “When we first saw it happening, we were frankly in disbelief,” said Dr. Sushanta Mitra, professor of mechanical and mechatronics engineering and executive director of the Waterloo Institute for Nanotechnology. “We double-checked everything because it seemed to defy common sense. There was excitement in the lab when we confirmed it wasn’t a fluke and that this was real vertical rolling.” The researchers discovered that the ball’s rigidity played a crucial role in determining whether it would fall or stick. Too rigid, and it fell. Too adhesive, and it stuck. However, when the sphere was as elastic as a gummy bear, and the surface was as soft as a mousepad, the pea-sized ball rolled down the vertical surface at a speed of approximately one millimetre every two seconds. “The key is that as it rolls, the sphere slightly changes shape at the contact point,” Mitra explained. “The front edge acts as a closing zipper, while the back edge acts like opening it. This asymmetry creates just enough torque, or grip, to maintain rolling without either sticking or completely falling off.” While there are no immediate practical applications—don’t expect to be bowling down skyscrapers anytime soon - the research could have far-reaching implications for robotics. The team believes their findings may lead to the development of soft robots capable of sliding down pipes or navigating cave systems, as well as exploring potential uses in Mars missions. “This opens up a whole new way of thinking about movement on vertical surfaces,” Mitra added. “Currently, robots and vehicles are limited to horizontal or slightly inclined surfaces. This discovery could change that.”
Keywords: feature,photo feature,photo story,Physics,vertical rolling,gravity,University of Waterloo,breakthrough,soft robotics,friction,elasticity,sphere,surface interaction,mechanical engineering,gravity defiance,soft-on-soft contact,torque,innovation,robotics,Mars missions,gecko locomotion,theoretical calculations,experiments,science,tech,technology,defying gravity
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