Original post:
This morning Improbable Research brings us:
Dropping and bouncing cats
A small collection of items about dropped and bounced cats:
1. ”Does a Cat Always Land on Its Feet?” [article in Annals of Improbable Research, vol. 4, no. 4]And the headline story, originally posted October 4, 2010:
2. The Cat Bounce web site.
3. Dead Cat Bounce, the stock market metaphor.
4. The physics of skulking and falling cats.
(Thanks to investigator John Runions for suggesting the conjunction of #1 and #2.)
What is the Terminal Velocity of a Cat?And from Ars Technica Christmas Day 2019:
I don't know, let's ask a physicist.
From the University of Alaska, Fairbanks:
Terminal Velocity
Terminal velocity, a rather chilling term, describes the velocity at which drag force from the air becomes equal to the force from the weight of an object, and thus the object no longer accelerates and consequently velocity remains constant. The greater an object's cross-sectional area and the less its mass, the lower the terminal velocity and the sooner it's reached. A cat reaches its terminal velocity of 60 mph within 5 stories of freefall. For comparison, a person's terminal velocity is 120 mph.Once a cat reaches its terminal velocity, it then begins to slow down. This is because the cat relaxes, changing its position from back arched, head down, and legs pulled tightly underneath its body, to resemble a spread eagle cat. This increases its cross-sectional area and slows the cat down. The reason for this is that our bodies are only sensitive to acceleration (this is why at times on an airplane flight it feels as if you aren't moving at all). Relaxing also causes the impact force to be spread out over more area when the cat lands, resulting in a decrease in injuries to cats' limbs when they fall seven or more stories.Professor Puss-Puss demonstrating L=mvr:
**This graph is taken from "How Cats Survive Falls from New York Skyscrapers." It plots the percentage of adult humans and cats killed by a fall versus the stories fallen. The adult human graph increases steadily to 100% while the cat graph increases to about 10% and then decreases to about 5% for falls from 7 to 9 stories. Although the graph doesn't show it, the survival rate holds steady at 95% from 9 to 32 stories.
Not only do cats seem to "understand" how increasing their area can lead to a less painful landing, they also seem to be well acquainted with the conservation of angular momentum, which they artfully use to land on their feet time and time again.
:The paper that made curiosity about falling cats a legitimate area of academic study:
High-rise syndrome in cats (1987)Which supplied the data illustrated by the curve, above.
However, as The Straight Dope points out:
...The potential flaw is this: the study was based only on cats that were brought into the hospital. Clearly dead cats, your basic fell-20-stories-and-looks-like-it-came-out-of-a-can-of-Spam cats, go to the Dumpster, not the emergency room. This may skew the statistics and make falls from great distances look safer than they are....Research at the University of Zagreb, "Feline high-rise syndrome: 119 cases (1998-2001)" was inconclusive on the cat-in-a-dumpster hypothesis.
I believe this demonstrates that most market drops are survivable.
Next: The Bounce
The surprisingly complicated physics of why cats always land on their feet
Ars chats with physicist Greg Gbur about his book, Falling Felines and Fundamental Physics
Scientists are not immune to the alluringly aloof charms of the domestic cat. Sure, Erwin Schrödinger could be accused of animal cruelty for his famous thought experiment, but Edwin Hubble had a cat named Copernicus, who sprawled across the papers on the astronomer's desk as he worked, purring contentedly. A Siamese cat named Chester was even listed as co-author (F.D.C. Willard) with physicist Jack H. Hetherington on a low-temperature physics paper in 1975, published in Physical Review Letters. So perhaps it's not surprising that there is a long, rich history, spanning some 300 years, of scientists pondering the mystery of how a falling cat somehow always manages to land on their feet, a phenomenon known as "cat-turning."
"The falling cat is often sort of a sideline area in research," physicist and cat lover Greg Gbur told Ars. "Cats have a reputation for being mischievous and well-represented in the history. The cats just sort of pop in where you least expect them. They manage to cause a lot of trouble in the history of science, as well as in my personal science. I often say that cats are cleverer than we think, but less clever than they think." A professor at the University of North Carolina, Chapel Hill, Gbur gives a lively, entertaining account of that history in his recent book, Falling Felines and Fundamental Physics.
Over the centuries, scientists offered four distinct hypotheses to explain the phenomenon. There is the original "tuck and turn" model, in which the cat pulls in one set of paws so it can rotate different sections of its body. Nineteenth century physicist James Clerk Maxwell offered a "falling figure skater" explanation, whereby the cat tweaks its angular momentum by pulling in or extending its paws as needed. Then there is the "bend and twist" (not to be confused with the "bend and snap" maneuver immortalized in the 2001 comedy Legally Blonde), in which the cat bends at the waist to counter-rotate the two segments of its body. Finally, there is the "propeller tail," in which the cat can reverse its body's rotation by rotating its tail in one direction like a propeller. A cat most likely employs some aspects of all these as it falls, according to Gbur.
Gbur is quick to offer a cautionary word of advice to anyone considering their own feline experiments: "Please don't drop your cats!"—even in the name of science. Ars sat down with Gbur to learn more about this surprisingly prolific area of research.
Ars Technica: What led you to write an entire book about the physics of falling cats?
Greg Gbur: It really started with my love of the history of science and writing about it on my blog. One day, I was browsing old science journals, and I came across an 1894 paper about photographs of a falling cat landing on his feet. I wrote a blog post about it. But I wasn't completely satisfied with the explanation, and I realized there were more papers on the subject. Every time I did a search, I found another paper offering another angle on the problem. Even in the last few weeks of writing the book, I still kept coming across minor little papers that gave me a little bit of a different take on the history. It was surprising just how many papers there were about the falling cat problem. The more you look, the more you find people intrigued by how a cat lands on his feet. It seems like a problem that would be readily solvable.
Ars: Surely one of the issues was that photography hadn't been invented yet, particularly high-speed photography.
Gbur: Yes. Maxwell did his own preliminary investigations of the subject, but he pointed out that when you drop a cat from roughly two feet, it can still land on its feet, even if you're dropping it upside down. That's a really short period of time. The human eye simply can't resolve that. So it was a problem that was largely not solvable until the technology was there to do high speed photography.
Étienne-Jules Marey did the first high speed photographs of falling down. It was almost an afterthought for him. He was doing all these different high-speed photographs of different animals, because that was his research, studying living creatures in motion. He presented the images of a falling cat, and it genuinely shocked the scientific community. One of the members at the meeting where the photographs were presented, said (and I paraphrase), “This young Marey has presented us with a problem that seems to go against the known laws of physics."
The motions that are depicted in the photographs are quite complicated. The explanation given is part of the truth, but it seemed incomplete. It was good enough to convince physicists that a cat wasn't violating the laws of physics, but it wasn't good enough to convince everyone that it was the right explanation, or the complete explanation.....MUCH MORE
Ars: You summarize four distinct hypotheses offered at various times to explain the phenomenon of cat turning. So what is the best explanation we have so far for how a cat can turn and fall and land on its feet?....
