See for yourself how changes in air pressure cause wind. There is air pressure all around us which means that the weight of the molecules in the air are always pushing down toward the Earth. Or being pulled down with gravity! The air pressure isn’t always the same though. That’s why you hear the weather people on TV talk about areas of high pressure and low pressure. High pressure is when there are a lot of air molecules and low pressure is when there are less air molecules.
- 2 cardboard toilet paper tubes
- Drinking straw
- A flat, level table or surface (like a big book)
What to do
Place the two cardboard tubes about an inch apart. With the straw, blow a steady stream of air between the tubes. What happens?
When you are blowing a stream of air between the tubes, the moving air is creating lower pressure, or less molecules. The air outside of the tubes is a higher pressure, or more molecules and those molecules rush in to take the place of the ones you blew away. Those rushing air molecules, or wind, caused the tubes to roll together! See if you can make other lightweight objects move using Bernoulli’s Principle!