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Heavy rocks could also bounce over water, physicists say: NPR

Heavy rocks could also bounce over water, physicists say: NPR
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Flat, light rocks like the ones pictured above are preferred for rock jumping. A new study has found that heavier rocks can also skim the water surface.

Jeff J Mitchell/Getty Images


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Jeff J Mitchell/Getty Images


Flat, light rocks like the ones pictured above are preferred for rock jumping. A new study has found that heavier rocks can also skim the water surface.

Jeff J Mitchell/Getty Images

When skipping a rock over water, most people look for flat and light rocks. Now, a new study suggests that curvier, heavier rocks can also yield impressive jumps. And these insights will not only help you improve your game, they could also be applied to the real world, such as making airplanes more efficient.

Ryan Palmer is an applied mathematician at the University of Bristol in the UK and a co-author of the study. released this month in the Royal Society.

He and his colleague created a model to learn how shape and mass affect the way objects interact with water. They found that when jumping rocks across a lake, “if you pick something heavier, you get what’s called a superelastic response,” Palmer said.

In other words, a heavier object could give an impressive bounce.

“What happens is the rock bottoms out on top of the water layer, and because it’s heavier, it sinks further down and stays in contact longer,” Palmer said. “This increases the pressure on that rock, which then increases the force lifting it out, and you can get an almighty leap in that response.”

Well, Palmer admitted that while heavier rocks can give you a big jump, they don’t result in as many jumps as flat ones. The results also depend on the shape of the stone, as a stone that is too heavy may not work.

“So the takeaway really is that a heavier rock that might sink if it’s curved a little more might be more likely to overfly,” he said.

However, Palmer and his colleague studied more than just the physics of stone jumping. They used the mathematical model to better understand aircraft icing, a phenomenon that occurs when aircraft fly through very cold weather.

Sometimes puddles of water form on the wings of an airplane, and ice crystals in the air can come with them and either sink into that puddle or drain away. If they sink, they lead to ice formation, which can be dangerous.

But when they skim, Palmer said, “Well, it’s pretty much the same physics and dynamics that you might find when you pick up a rock and try to throw it across a lake.”

Palmer said it’s important to know where the ice might be going to better understand if other parts of the plane need more protection.

He also insisted that airliners are safe; There are systems in place to protect them from dangerous ice formation. His research aims to increase the efficiency of these protective measures.

“Where we live in this world of climate change and rising fuel costs and stuff like that, you’re actually always trying to be more efficient, so you can design your systems better and protect planes better,” he said. “They can efficiently and innovatively cover those odd situations that can arise.”

And while Palmer looked for practical applications, that wasn’t the only thing he took away from his research.

“Since I started this work, skimming rocks and especially picking the slightly weirder rocks has become even more irresistible,” he said. “Which aren’t necessarily that flat.”

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