The Physics of Flight

Our class had a special visitor yesterday: Jamie Saxon, who is a graduate student in physics at the University of Pennsylvania, came in to talk with the kids about some of the physics behind flight. Last Friday, the whole school had watched a DVD called The Way Things Work: Flight, which mentioned that it is the faster movement of air over the top of a wing that creates lift. So, Jamie spoke with the children about the nature of pressure and force, the energy contained in objects of various masses and positions, and the conservation of energy. In the end, we had arrived at a simplified form of Bernoulli's equation, which describes the relationship between high speed (velocity) and low pressure: P + ¹/₂ρv² = Constant

(P = pressure, ρ = density, v = speed)

Understanding pressure by experimenting with lifting a table in the kitchen:

it was much easier when more people helped, spreading the force required over a greater area!

We pushed around a desk to learn about the nature of work (being force multiplied by distance)...

and in the process learned some things about the nature of equations.

Using balloons, funnels, and ping-pong balls, we learned that by blowing or pushing air through an inverted funnel, you can hold a ping-pong ball up inside the funnel—despite the fact that you're blowing down on it! The ball is held up by the low pressure area created by the fast movement of the air on either side of it. You can try this at home: all that's really needed is a funnel and a ping-pong ball!

In the end, each of the children got a strip of paper to take home, with Bernoulli's equation printed on one side and the terms of the equation defined on the back. If you blow across the top of the strip when it's hanging in your hand, the paper will rise—not because the air is slipping around to push it up from the bottom, but because you're creating a low-pressure zone above it!