[thedoc (OP)]

Find out how to build an airbrush to produce beautifully smooth paint finishes, and what this has to do with a car engine.

Read more about this kitchen science experiment.

Listen to the Experiment [chapter podcast=2174 track=09.11.29/Naked_Scientists_Show_09.11.29_5057.mp3","]_{Part 1}[/chapter] [chapter podcast=2174 track=09.11.29/Naked_Scientists_Show_09.11.29_5071.mp3","]_{Part 2}[/chapter] [chapter podcast=2174 track=09.11.29/Naked_Scientists_Show_09.11.29_5057.mp3][/chapter]
...or download as MP3 [1] [2]

[Karen W.]

This would make a great science and art project for kids.. combine two in one... Very cool Dave and I love the text boxes opening up at the straw so it refreshes the text and reiterates whats happening.. very nice set up Dave!

[John]

It's easier if you don't cut fully through the straw...

[Stuti]

Here's a really good application to Bernoulli's theorem.Good work.

[Madidus_Scientia]

Why is fast moving air at a lower pressure?

Air being a gas can only be accelerated by a change in pressure. If the air is slowing down then it must be going from an area of low pressure to a higher pressure, so the rapidly moving air must be at a lower pressure than the slower moving air.

I don't get it. If you spray a stream of air from a high pressure tank it slows down, but it's moving from high pressure to the lower pressure atmosphere?

[SteveFish]

The fast moving air in the straw certainly has a lower pressure than the slower moving air in the mouth and lungs of the kitchen scientist, but once the air exits the straw it immediately drops to ambient pressure. Moving free streams of air don't have a lower than ambient pressure. Using the Bernoulli effect to explain air brushes, perfume sprayers, and flit guns as well as movement of empty pop cans, ping pong balls, various pieces of paper when subjected to a free air stream, as a demonstration of the Bernoulli effect is widespread on the internet, but they are all wrong. This is a science site and should get it correct.

As a good scientist (retired) I can provide evidence, and the following links should warm the heart of any kitchen scientist. The first is a teaching demonstration on the website of the Department of Physics at the University of Maryland, USA.--
http://www.physics.umd.edu/lecdem/services/demos/demosf5/f5-12.htm

This next set of demonstrations are very neat. They are in the process of being created by John Welch, the Physics Lab director at Cabrillo College in California, USA. The videos are on a link on this page--
http://www.cabrillo.edu/~jwelch/bernoulli/bernoulli-coanda.html

I can help explain how these demonstrations, how the incorrect ones on the web, and shamefully in some textbooks, are actually working if need-be. Steve

[drifter]

Hi

Another article from the website mentioned by the author above as proof seems pretty adamant that this is not the Bernoulli effect:

http://www.physics.umd.edu/lecdem/services/demos/demosf5/f5-10.htm