If the rigid ball is placed on a rigidly slanted surface, gravity will cause it to roll down the surface. But what happens if the surface or plane is completely perpendicular? Researchers have previously assumed that without the initial push, the ball would not fall directly to the ground without rolling. However, the new research only redefines this belief, as well as long-term assumptions in the field of physics.
Researchers at the University of Waterloo reveal the exact situation that causes the sphere to roll towards the vertical plane without physical intervention. While this niche observation seems to be out of touch with everyday life, it may have useful applications for exploring hard-to-reach areas such as pipes, caves and even spaces.
“We frankly illustrate this when we first saw this,” Sushanta Mitra, executive director of the Waterloo Institute of Nanotechnology, said in a university statement. The researchers described their findings as a challenge of “our basic understanding of physics.” They “scrutinized everything carefully because it seemed to ignore common sense. It was exciting in the lab when we confirmed that this wasn’t a flu worm and that’s really vertical scrolling.”
Mitra and his colleagues accidentally grabbed the vertical scroll with a high-speed camera and explained their findings in a study published in the journal Soft Matter in April.
In their experiments, vertical scrolling depends on the precise balance of softness (with elasticity as elastic), which is between a small ball and a vertical phone-sized surface. When the spheres are too firm, they just fall directly to the ground. On the other hand, when they are too soft, they either slide down without rolling or stick to the plane. However, every two seconds, the spheres that approximate the soft bear spontaneously roll at about 0.039 inches (one millimeter) at about 0.039 inches (one millimeter).
“The key is that as it rolls, the shape of the ball changes slightly at the contact point,” Mitra explained. “The front edge acts as a closed zipper, while the rear end acts like opening it. This asymmetry creates enough torque or hold to keep the rolling without sticking or falling completely.”
The team’s findings could have practical implications for the creation of soft robots that can extend vertical walls to explore or monitor infrastructure and natural environments that are inaccessible to the Earth. “This opens up a whole new way of thinking for motion on vertical surfaces,” Mitra continued. “At present, robots and vehicles are limited to horizontal or slightly slanted surfaces. This discovery may change that.”
