Textbooks and Internet Bernoulli sites present many experiments to demonstrate Bernoulli's Principle. These experiments rarely demonstrate Bernoulli's Principle at all. They demonstrate Radial Momentum.

As high school students must learn, the standard explanation for lift is Bernoulli's Principle; high velocity means low pressure. While Bernoulli's Principle is fundamentally correct, the application of it to explain lift is fundamentally incorrect. The real principle behind lift is Radial Momentum. Ironically, Bernoulli's principle does not even explain the devices commonly used to demonstrate the Bernoulli Principle itself.

The Radial Momentum theory explains all of the experimental observations of pressure decrease in open systems with flow motivation. It explains atomizers, airfoils, airplanes, curve balls, lift, cavitation, eddy currents and a full range of behavior involving pressure decrease.

Bernoulli's Principle does not explain the experimental observations, particularly those differentiating between radial flow and non-radial flow in open systems with flow motivation. Bernoulli's Principle is widely misapplied. Ironically, Bernoulli's Principle does not explain the experiments commonly used to demonstrate the Bernoulli Principle.

 Flying Paper Note: This experiment comes, complete with Bernoulli misapplication, from NASA. Flying Paper Materials: 2" x 8" strip of paper & paper clips Experiment: Place the strip of paper so that one end is resting just under your lower lip and the other end is hanging down. Holding it in place, blow over the top of the paper. The end of the strip of paper hanging down will lift up so that it is "flying." Try placing paper clips on the hanging end of the paper and see if it has enough lift to overcome their weight. Explanation: With the increased air speed over the top of the paper, the air pressure over the top of the paper is decreased (Bernoulli's Principle). This makes it so that the paper has higher air pressure underneath it, lifting it into the air. Bernoulli Faster flowing air over the top of the strip of paper causes lift and the paper rises Radial Momentum I hold a strip of paper against my bottom lip and blow air across the top. Radial Momentum induces a region of low pressure above the strip and the higher pressure under the strip elevates it.

 Floating Tennis Ball Bernoulli Faster air inside the cone keeps the ball inside the cone Radial Momentum The effluent stream from a vacuum cleaner is seen to hold a ball aloft, even if the air stream is tilted somewhat off true vertical, in which case the ball may spin rapidly. Radial Momentum induces a region of low pressure inside the cone that keeps the ball inside the cone. Higher air velocity at the center of the cone spins the ball.

 Atomizer Bernoulli Faster air over the nozzle sucks the perfume up the tube. Radial Momentum In a perfume atomizer, the air supply from a squeeze ball, flows over a delivery tube. Radial Momentum induces a cone of low pressure that acts to elevate the perfume into the flow. Atomizers work with an air supply (that expands radially) and do not work with a liquid supply (that does not). An atomizer nozzle that entrains flat and expanding flow is more efficient.