# PIng Pong Pressure

Air moves from high to low pressure, but what about the actual movement of air: wind?

We have all experienced wind and, like it or hate it, it affects us. Moving air can jostle your hair about, fly a kit, or, in extreme cases, tear entire buildings from their foundation. Did you know that this moving air actually creates low pressure, though? It's true. On an exceptionally windy day, you can even see tall buildings bowing towards each other near their tops! We're going to recreate this phenomenon using ping pong balls in the Ping Pong Pressure experiment.

## Experiment Materials

• Modeling clay
• Hairdryer
• Straws
• Ping pong balls

# Experiment

1. Place the one end, each, of two straws into large pieces of clay. When the straws have been stuck into the clay, the straws need to stand upright.
2. Mold two, smaller pieces of clay around “the bottom” of two ping pong balls.
3. Place the ping pong balls, clay down, on top of each of the two upright straws. Position the balls so that the are as level as possible.
4. Make sure that the straws are able to move within their clay base.
5. Plug the hairdryer into the wall and turn it on.
6. Aim the hairdryer's stream of air directly between the two ping pong balls. You'll witness the ping pong balls draw together.
7. Position the hairdryer and different angles to see if the ping pong balls still push together.

# How Does It Work?

As you positioned the stream of air to blow between the balls, you witness them draw together. This is a fantastic demonstration of Bernoulli's principle. Bernoulli observed that fast moving air creates an area of low pressure. The low pressure between the ping pong balls allows the higher pressure outside of the balls to push them towards each other. The same effect can be observed in water currents.