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I made a new version of the falling cat video, with narration. It explains how cats turn around while having zero net angular momentum during the fall:
It is easier to grok, when you imagine the cat bends 180° into a U-shape. Then its obvious that the ends of the U have opposite angular momenta. But real cats do not bend than much, so you need vectors.anorlunda said:Wow. That's very clever. I'll have to re-watch it several times to grok the zero total.
My video explains the core mechanism of how it is possible physically. Nature, especially biology is always more complex. The motion of a real cat's halves is often less symmetrical, which is likely dictated by physiology and preferred landing pose to dampen the impact better.Spinnor said:I don't who is right I am just suspicious of the answer given by A.T., the first video of the falling cat does not seem to jive with A.T.'s explanation. Maybe a combination of both explanations?
A.T. said:My video explains the core mechanism of how it is possible physically. Nature, especially biology is always more complex. The motion of a real cat's halves is often less symmetrical, which is likely dictated by physiology and preferred landing pose to dampen the impact better.
You're welcome. Both Destin and Mark Rober in the videos linked above correctly point out that real animals sometimes turn around the front of the body first, then the back, by varying the moments of inertia. Likely because they prefer to see where they are going and/or want to land on a certain pair of legs first. But in other videos, especially when a cat falls from a small height and has to turn very quickly, it is more symmetrical like in my video.Spinnor said:I got distracted looking for differences in the video I posted and forgot to like your video which immediately makes clear the general physics of the cats motion. Looking at old posts of mine gave me another chance to like a great video. Thanks.
when are you going to do a simulation summersalt ( somersault - phonetics is great ) with twist off the diving board.A.T. said:You're welcome. Both Derek and Mark Rober in the videos linked above correctly point out that real animals sometimes turn around the front of the body first, then the back, by varying the moments of inertia. Likely because they prefer to see where they are going and/or want to land on a certain pair of legs first. But in other videos, especially when a cat falls from a small height and has to turn very quickly, it is more symmetrical like in my video.
256bits said:when are you going to do a simulation summersalt ( somersault - phonetics is great ) with twist off the diving board.
Here some math people envision a 1.5 rotation with 5 twists as being possible.
https://www.technologyreview.com/20...ly-new-dive-with-5-twists-and-15-somersaults/
A PDF from the arxiv
https://arxiv.org/abs/1612.06455
256bits said:when are you going to do a simulation summersalt ( somersault - phonetics is great ) with twist off the diving board.
Here some math people envision a 1.5 rotation with 5 twists as being possible.
https://www.technologyreview.com/20...ly-new-dive-with-5-twists-and-15-somersaults/
A PDF from the arxiv
https://arxiv.org/abs/1612.06455
Well, height here is just a proxy for time. One easy way to increase time is to be in free fall, for example in orbit at the ISS or parabolic flight.Spinnor said:One limiting factor in the above analysis of the number of possible twists is platform height.
In the below parabolic flight video at 0:11 a cat makes ~8 rotations in 5sec.Orodruin said:Well, height here is just a proxy for time. One easy way to increase time is to be in free fall, for example in orbit at the ISS or parabolic flight.
According to the principle of conservation of angular momentum, the total angular momentum of a system remains constant unless an external torque is applied. In the case of a falling cat, the initial angular momentum is zero, but as the cat starts to rotate its body, its angular momentum increases. However, the cat also rotates its legs in the opposite direction, canceling out the angular momentum of its body and resulting in a net zero total angular momentum.
Cats have a unique ability to twist their bodies in mid-air, allowing them to land on their feet when falling. This is due to their flexible spine and strong hind legs, which enable them to rotate their body quickly and maintain their balance. Additionally, cats have a highly developed inner ear that helps them orient themselves in space and adjust their body position while falling.
While cats have a remarkable ability to rotate and land on their feet, they can still get injured when falling from a significant height. The impact of landing can cause broken bones, internal injuries, or even death. Additionally, if a cat does not have enough time to rotate its body, it may not be able to land on its feet and could still get injured.
Cats are not the only animals that can rotate while falling. Some species of rodents, such as squirrels and rats, also have the ability to twist their bodies and land safely on their feet. Additionally, certain birds, such as owls and hawks, have a similar ability to rotate their bodies while flying and landing.
The falling cat phenomenon has been studied in various fields, including physics, biomechanics, and robotics. Understanding how cats rotate while falling can provide insights into the principles of angular momentum and help engineers design more stable and agile robots. Additionally, studying the cat's ability to land on its feet can also inform the development of safety mechanisms for human falls.