In your childhood days, you must have tried sending a disk-shaped stone to skip across the surface of the water multiple times. Researchers now reveal why is it so easy to get such impressive water-skipping performance from an elastic ball with only a mediocre launch.
Researchers at Utah State University’s college of engineering have unraveled the physics of how elastic spheres bounce on water more easily than rigid ones.
This may offer new insight into water impact physics – an important area of study in naval applications and maritime and ocean engineering.
The team uses high-speed cameras to capture images of elastic spheres bouncing across tanks of water in a laboratory.
They found that elastic spheres skip along the water surface by deforming into an ideal disk-like geometry that resembles a stone one might find near the shore.
Due to the sphere’s deformed shape, the water exerts a larger lifting force on elastic spheres than stones.
Truscott’s study not only reveals the physics of how elastic spheres interact with water, but also predicts how many skips will occur.
“Our approach was playful at first. In general, I have always found that childish curiosity often leads to profound discovery,” said Tadd Truscott, assistant professor of mechanical engineering.
In addition, the team found that elastic spheres can bounce off the water surface from much higher impact angles compared to rigid spheres – a big clue into why these elastic objects are much easier to skip.
Skipping objects along the water surface has a wide range of applications from simple aquatic toys to naval operations.
“The study also provides insight into methods for modeling objects that interact with the water surface and have elastic responses to the surface like rubber boats, tubes, wakeboards and water skis,” Truscott explained in a paper appeared in the journal Nature Communications.