Why do cats always land from their feet

Where a cat falls from a high placeHigh speed cameraIf you take a picture with slow motion, you can see clearly what kind of principle the landing is done from the feet.

High Speed ​​Video of Flipping Cats | Smarter Every Day 58 (Cute Cat vs Physics) - YouTube


"Explaining familiar science in an easy-to-understand manner"Smarter Every Day"The challenge this time is to clarify the situation of cats landing on the ground using high speed cameras and to clarify by looking at slow motion, with the question" Why do cats always land from their feet? "


In fact


I am having a stunt cat come.


It is Jiji.


Shooting is done with this high speed camera.


Slow motion of the taken picture is here. First catch the legs of a cat, lift it to the height of your face, and release your hand.


While falling, cats gradually rebuild their posture ......


The feet are facing the ground when falling down to around the waist.


By the time it approaches the ground, it is almost completely landing posture.


Don


As if nothing happened to Pune and somewhere.


The cat first grasps which direction is up using the gyro sensor of the eyes and ears. However, I do not know the details at this stage as to how to make the body rotate, although I know how to catch the direction.


I will look at it from another angle.


The cat first twists the upper body ......


Next, I am twisting the lower body. Both legs turned to the ground with this.


Enter the landing posture as it is ... ...


Well.


"I understood the interesting thing, the cat does not rotate the body at the initial stage of falling.When I fall, I begin to rotate my body, and at the final stage of the fall I managed to rotate it It is stopping.First law of Newton's movement (law of inertia)According to, the stationary object should remain stationary as long as there is no external force action. Even though no external force is supposed to act on cats, why does it happen? I do not understand anything at all. "


Cats are thought to rotate the body by rotating the tail, but it is not actually the case. Because a cat without a tail can also land properly.


For example, in a state of weightlessness, cats can understand that even if they rotate the tail, they are not properly rotated. In other words, it can not be explained by rotating the tail.


Actually the back is not the tail but the point. The cat rotates the body by bending the back, making it to rotate only half of the body first.


Let's take a closer look. First of all, grasp the ground which is visually, or using the gyro sensor function of the ear.


I will look at the inertia of the upper body and the inertia of the lower body. Initially, the forefoot is contracted and the hind legs are stretched.


If the direction of rotation of the upper body is defined as forward rotation, inertia acts on the lower body in the negative rotation direction on the opposite side, but because the front leg is in a contracted state, the moment of inertia is small and conversely the rear leg is stretched so that the moment of inertia It is getting bigger. As a result, even if you rotate the upper body a lot, the rotation of the lower body in the opposite direction decreases.


Align the back legs towards the center axis.


Here, with the forefoot stretched out, the rear foot swiftly.


If the rear leg is folded in the body, then the moment of inertia of the upper body increases and the moment of inertia of the lower body decreases, on the contrary. For this reason, even if the lower body is rotated a large amount, the return of the upper body becomes smaller.


This completes the rotation of the body, the rest is extended toward the landing, the rear leg and the tail are extended.


We are ready for landing.


And at the moment of landing we use four feet to absorb the shock.


In short, by bending the body and changing the moment of inertia, we are causing rotation,Cats twistIt seems to call it. Terrible cat's power.