Ask me anything Month

Right, so "Ask me anything month" is coming to a close, and no one has asked me questions!

Here's your last chance. :)

Question #1

oakleaves asks me:
"What's the average velocity of a laden swallow?"

Using my psychic skills, I surmise that you are making a reference to the Monty Python movie, The Holy Grail. There is some question in that movie as to whether we are talking about a European or African Swallow, but in fact, the African Swallow in question is non-migratory.

An average unladen swallow has an airspeed of 11 m/s, or 24 mph.

Of course, semantically speaking, you didn't ask for the velocity of an average swallow, but rather, the average velocity of a swallow, two very different things. It depends on what swallow we're dealing with, in fact! Not all swallows are created equal, you know. However, for expedience, I will assume that our swallow is relatively average.

To calculate the average velocity of a laden swallow, however, requires a great deal more information.

(1) How many rest breaks is the swallow taking? I know when I go on long trips, I like to stop and stretch my legs. And I'm not even traveling under my own power! This would affect the AVERAGE velocity.
(2) Airspeed and velocity are not the same thing. Velocity is affected by the windspeed over the course of the trip, and without knowing the windspeed, we can't actually calculate the velocity.
(3) For that matter, velocity is a vector (whereas speed is a scalar). Vectors have direction. In order to determine the velocity, we need the start and end point of the trip. If we are considering the entire trip from Europe to Africa and back to Europe, then the total velocity was in fact zero. Lucky for you, you were clever enough to ask about the AVERAGE velocity, which is NOT a vector. This is calculated by integrating the velocity as a function of time over the course of the trip [that is, v(t) dt from t=beginning to t=end]. Since we're assuming that we have an average swallow, this should work out to the same as the aforementioned speed of 11 m/s.
(4) And finally, the question of how laden the swallow is. This depends on what the swallow is carrying! The weight will slow it down and tire it out, leading to more rest breaks. And the shape of the object could potentiall introduce a significant drag factor, slowing the swallow down a great deal.

In Monty Python, the assumption is that the swallow is carrying a single coconut, which I am able to estimate will weigh between 300 and 400 g. However, the European Swallow only masses about 20 g. Therefore, it is safe to assume that a swallow laden with a coconut would have no average velocity, as it would be unable to take off.

If you would like a less serious answer, click here. It addresses only the unladen swallow, but it is nonetheless amusing. :)