Why can a ball still float in a column of air, even at an angle?
Have you ever heard the phrase, “getting caught in the slipstream?” This typically refers to a situation in which outside forces keep something or someone in a particular position. During today’s experiment, you will observe that phrase in action as we explore the famous Bernoulli Principal. This is the reason airplanes are able to stay aloft, and what keeps birds fluttering away. See if you can handle the pressure in this week’s activity!
Daniel Bernoulli was a Swiss scientist and mathematician who documented important scientific principles in the eighteenth century. Particularly interesting was his work in fluid dynamics, by which the Bernoulli Principle was discovered. While Bernoulli discovered that pressure decreases when the flow speed increases, it was actually a man named Leonhard Euler who figured out Bernoulli's equation in 1752. Nevertheless, Bernoulli's work influenced pivotal technology that has changed our world forever, from carburetors in vehicles to airplane wings.
You should be able to tilt the hair dryer pretty far before the ball actually falls out of the column. This is because the ball is actually held in the column by the pressure of the air around it. The Bernoulli Principal tells us that moving fluids- like gasses or liquids- have lower pressure than fluids that are not moving. When you turn the hair dryer on, you are creating a column of moving air, which has a lower pressure than the air around it. When the ball starts to move out of that column, the high-pressure air outside the column pushes it back into the column. This still happens even when you tilt the column, so you can tilt pretty far before the ball starts to fall, even though it isn’t being pushed straight up by the air anymore.
The Bernoulli Principle is also what causes a shower curtain to move into the shower when you turn on the water. The moving water and air create a low-pressure space, and the high-pressure air outside the shower pushes into that low-pressure area. As it pushes, it brings the shower curtain with it, so the curtain moves toward the inside of the shower.
Remember to clean up when you are done. Put the hairdryer and ping pong ball back where you found them.
Build a ping pong ball launcher like in the video, using construction paper and tape.
The Bernoulli Principal works with all fluids- both liquids and gasses. To see the Bernoulli Principal work in liquids, try floating some cereal like Cheerios about two inches apart in a bowl of water, and pour a small stream of water in between them. The Cheerios should move toward each other because the moving water in creates a low-pressure area.
You can also try tying two balloons to some string, and hanging them a few inches apart, and blowing in between. The balloons should move towards each other, just like the cheerios.
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.