Skipping a stone on water requires a flat, disk-like stone thrown at a shallow angle, but elastic spheres are remarkable skippers, too, even at higher impact angles. Researchers at the Splash Lab have just published their work on why these balls skip so well. As seen in the top animation, the elastic spheres deform on impact, flattening to a more disk-like shape that rides at an angle of attack relative to the air-water interface. Both features are important to the spheres’ enhanced skipping. By flattening, the sphere comes into greater contact with the water and by orienting at a larger angle of attack, the sphere increases the vertical component of force the water generates on the sphere. It’s this vertical force that lifts the sphere up and lets it keep bouncing.
Because the ball is soft, it keeps deforming after its impact and bounce (see top animation). For some skips, the timescale of the sphere’s elastic waves is smaller than the length of time the sphere is in contact with the water. When this is the case, the sphere’s elastic waves will affect the impact cavity in the water, forming what the researchers call a
matryoshka cavity, after the Russian nesting dolls. An example is shown in the second animation. For more, check out the USU press release, the original paper, or the award-winning video they made a few years ago. (Image credits: J. Belden et al./The Splash Lab)
I’m at the point where I’m skipping class because I feel lonely or not in the mood, smiling when I’m sad, reading through old texts to rekindle feelings of being wanted, and relying on music to comfort me when nobody else will…
One of our biggest hauls EVER! And so healthy. Including 36 boxes of blueberry´s. Some fruitarian days are coming up.
We could take 10x more than what we find dumpster diving now, but leave it because we just can’t eat it all. There is so much food going to waste it makes my head spin. Sometimes we hand things to strangers on the street or share it with friends. We used to leave things for other dumpster divers but found that there is so much food being thrown away that that is not necessary. If we empty 1 bin, the bin around the block will still be full.
We do use 95-100% of the things we find. Sometimes things go bad faster than we thought, but we have learned to be very inventive. We freeze, dry and juice things, make smoothies, jam, soups and sauces so things keep longer. We buy almost nothing at the supermarket anymore and have been eating healthy and a lot.