Bernoulli Balance

• Quicklinks:
• Background
• Key Concepts
• Materials
• Safety
• Standards

Background

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.

Key Concepts

• Air Pressure
• Bernoulli Principle
• Fluid Dynamics

Materials

• An adult helper
• Ping pong ball
• Hair Dryer
• Construction Paper (optional)
• Tape (optional)

Preparation

• To use the hair dryer, plug it in with the help of an adult.
• Make a prediction: What will happen to the ball when you turn on the hair dryer and place the ball in the stream of air? What about if you tilt the stream of air holding the ball up?
• Position the hair dryer so that when you turn it on, the air that comes out will be moving upwards.
• Turn the hair dryer on facing straight up and hold the ball in the stream of air. Then, let go of the ball.
• Try tilting hair dryer so the ball is floating at an angle instead of straight up and down. How far over can you tilt the hairy dryer before the ball falls out of the stream of air?
• Remember to clean up when you are done. Put the hairdryer and ping pong ball back where you found them.

Observation and Results

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.

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.

Safety First and Adult Supervision

• Follow the experiment’s instructions carefully.
• A responsible adult should assist with each experiment.
• While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
• Adults should handle or assist with potentially harmful materials or sharp objects.
• Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.

Next Generation Science Standard (NGSS) Supported - Disciplinary Core Ideas

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.

Engineering Design (ETS)1: Engineering Design