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Cats and Dogs Physics



Haven't you ever wondered why when a dog drinks water from a low bowl, its much messier than when a cat drinks from that same bowl?

Of course you haven't. But you're wondering now! So here's the physics explanation and a few accompanying videos.

The Answer: There's really not too much difference. Both the cat and the dog utilize the principal of water/liquid displacement in order to get the water to their mouths. The displaced water is then trapped in the "backwards spoon" that both animals create with their tongues. The difference between sloppy dog and cleaner cat is that the cat aims straight down (perpendicular) and uses less force to displace less water per drink while the dog uses more force to drink more water in less time. The dog also angles its head when drinking, and some water spills from the "backward spoon" as a result of earth's gravitational field imparting a force on the system. The most important difference is the force the dog uses to displace the water. The kinetic energy of the dog's tongue creates a wave in the water that sloshes all the way to the edge of a small bowl. When the crest of the wave reaches the bowl's edge: wet floor. The cat? There's just not enough force in the cat's drinking to create a wave to crest over the lip of the bowl. Remember, water molecules tend to hold their overall shape, so if at all possible, the water will fight to stay in the bowl.

I wondered if a cat the size of a greyhound would be just as sloppy as any dog, so I looked up the following video.


As you can see, this cat too drinks very neatly. But again, its simply because the cat uses less force to displace water with its tongue. Is drinking style an evolutionary trait? who knows, I'm just a physics student.


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