Cow Tipping - It's A Myth!

What better way to break up the monotony of important advances in elementary particles, of topological insulators, of neutrino physics, etc. then to talk about the myth of cow-tipping! This article in Modern Farmer collects up-to-date info on why this is a myth, including a physics calculation on what it would take to do such a thing, which would make it even more unlikely.

But say our hypothetical cow tippers got lucky enough to get close to a cow at night. There’s still the matter of the brute force needed to get the cow over. In 2005, University of British Columbia student Tracy Boechler and doctor of zoology Margo Lillie ran the numbers on cow tipping. Their findings? There’s no way one person could tip a cow. Two people? Maybe — but not in real world conditions.

“Two could do it in theory,” says Dr. Lillie. “But it’s not going to be easy, and as soon as the cow responds by bracing herself or leaning into you — which she will do — it will be even harder.” Cows, after all, stand on four legs and will quickly shift their weight to a wider, more stable stance if pushed against. And Lillie and Boechler’s calculations are based on an unmoving cow in equilibrium in which slow, steady force could be applied without pushback — an optimum (and unrealistic) state for cow tipping. Pull out your high-school text book and look up Newton’s Second Law: Force equals mass times acceleration. A cow has a lot of mass, and you’ll want to move that mass quite quickly, before the cow can react. Which means you’ll need to generate a lot more force. Per her calculations, that would require at least five, and probably more like six pushers. “It just makes the physics of it all, in my opinion, impossible,” says Dr. Lillie.

There ya go, kids! Don't try this at home, or more accurately, at a farm near you!

Zz.

The Physics of Drinking Dogs

We have now firm confirmation that dogs and cats drink alike!

Earlier on, there was a study on the mechanics of cats drinking water. It turns out that in a new study of dogs drinking water using high speed camera and x-ray images, dogs drink the same way as well!

This footage shows that as the tongue touches the surface of the water, the liquid adheres to it, creating a water column as the tongue is drawn back towards the mouth. The dog then snaps its mouth closed just as the water begins to fall backwards towards the bowl.

The research, published in the journal Biology Letters, has surprised scientists because it reveals that cats and dogs drink in the same way.

I'll post the exact citation to the paper when I find it.

Zz.

How Cats Drink

Hey, we seem to be getting quite a bit of pet physics lately. First we had the study on the wet-dog shake, which I thought was quite informative and entertaining. Now along comes a study on how cats lap at liquids when they take a drink[1].

Watching in slow motion reveals that cats of all sizes, from tabbies to tigers, have a very elaborate way of drinking. First, they move the tip of their tongue onto the surface of the water to flick the water up so that a little jet of liquid flies into the air. Then, in a flash, they catch the jet in their mouth.

So you can watch the motion of this yourself.


And now, for the dogs.


Zz.

[1] P.M. Reis et al., current published on Science Express.

The Wet-Dog Shake

Continuing with items on our physics of the mundane, which I really love, this time we have a rather amusing investigation. I'm sure most of us have seen this. A wet dog gets out of a pool or a water sprinkler, and gets ready to really shake its body to get ride of all that accumulated water. At what rate/speed does it shake its body to get rid of most of the water?

That is the study that was conducted by Andrew Dickerson and his colleague at Georgia Tech, and was published in Fluid Dynamics journal.

The team built a mathematical model of the processes involved, reasoning that surface tension between the water and the dog's hair is what keeps the dog wet. Overcoming that tension requires a centripetal force that exceeds it.

As centripetal force varies with distance from the centre of the creature, its radius is therefore crucial to work out the speed of the oscillations. The team arrived at an equation that calculates the frequency of that oscillation as R0.5.

To test that hypothesis, the team filmed a wide range of dogs shaking, and used the images to calculate the period of oscillation. For a labrador retriever, that turned out to be 4.3 Hz. He then expanded the search, filming animals as small as mice (27Hz) and as large as bears (4 Hz).

Here's the video that accompanied this article:



So the bigger the animal, the slower it can shake to achieve comparable drying, but the relationship isn't linear. Instead, it approaches a limit of 4Hz as an animal grows in size.

A preprint version of the paper can be found on Arxiv.

How many wet investigators that resulted in this study? :)

Can I say it once again how much I love things like this. You guys can go ahead and try to find the meaning of life, and why we're here, and how the universe began. Go at it and call me when you find out. But give me stuff like this that, while it appears to look mundane, can have wide-ranging application that most of us don't know about when we study such things. These things can be fascinating by itself, and the fact that they can have important implications for other systems is simply a pleasant bonus. Kids and students should be exposed to these kinds of curiosity, because these are the things that they can see and understand. Being curious and trying to understand how things happen is what physics is all about.

Zz.