Tuesday, July 10, 2012

It's quite hard to find the Wattage of a swan

So, a friend tweeted about liking the idea of a Mystery Swan, and tweeted "Is it a bird? Is it a plane?"

This naturally made me want to parody this classic:

I produced these tweets:

About 1% as fast a speeding bullet, more powerful than a hair drier, able to clear tall buildings with quite a few flaps... 
...Is it a bird? Yes! Is it a plane? No. It's Mystery Swan

They took me about an hour.

Now, finding out a swan's speed relative to a speeding bullet wasn't so hard. There were a number of sources for the speed of a swan, and I opted for 50 miles per hour.

Next is the speed of a speeding bullet. I figured I'd go for the fastest bullet out there, which come from rifles, and can be as fast as 1,500 m/s.

Now, I chose to go for a lower end of the scale for the swans, as my bullet source was old, but I liked it as it also mentioned Superman, and I figured guns may well have advanced.

The next bit was trickier. What is the power rating of a swan? Power is generally measured in joules per second, in a unit called the Watt.

Try as I might, I couldn't find anything on the power involved with a flying swan. So I changed tack.

Many websites told me swans eat around 8 - 9 kg of food a day, largely pond weed, and other river based insects and such. Finding the energy content of the food wasn't so hard.

Now, I didn't know the exact breakdown of the swan's diet, but taking a (rough, mental) average of the food available, it looked as if there was a round a little over 4 kcal per g of food.

Assuming the swan meets it's daily dietary needs, and isn't putting on, or losing weight, we can see that the swan consumes 150,624,000 Joules per day (by converting kcal to Joules and working out energy content for the kg consumed per day). Diving this by 86,400 give us the Joules used by a swan, per second, which works out as 1,743. Thus, the wattage of a swan is about 1.7kW. That's more powerful than a hair dryer, as they are around 1.5kW (or lower).

Now, this isn't the most rigorous of calculations, I'll admit, and you are more than welcome to improve upon it. But I'm quite satisfied with the accuracy needed for the, by now, over laboured joke. It's not as if I'm looking for the Higgs or anything.

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