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# Under (Air) pressure: Bernoulli's Principle

Difficulty: Easy

Duration: 60 minutes

Materials: Substantial

## Background

Did you know that many astronauts were airplane pilots before being recruited to go to space? This is a skill that is highly sought after by space agencies. Pilots understand their planes and the forces that are exerted on them during flight. One of those forces is lift. This activity explores the Bernoulli principle and how you can learn about lift using everyday objects.

The Bernoulli principle was established in by Daniel Bernoulli. This principle states that within the flow of a fluid, like a liquid or a gas, an acceleration (or increase in the speed of the fluid) occurs simultaneously with a decrease in pressure (or a decrease in the fluid's potential energy). In other words, Bernoulli's principle states that the higher the velocity of a fluid, the lower the pressure.

Bernoulli's principle can be applied to explain the operation of the wing of an airplane. The difference in the shape of the top and bottom of the wing influences the speed of the air flowing over the wing. (Remember, liquids and gasses are both considered fluids!) This creates a pressure difference in the airflow that produces the lift exerted on the aircraft.

Under the wing, the speed of the air is not influenced by the flat profile of the wing. Conversely, the curved profile on the top side of the wing travels a greater distance through the air. This increases the speed of the airflow, thereby creating a zone of low pressure.

This pressure difference (normal pressure below the wing and low pressure above the wing) causes an upward force and produces the lift of the aircraft. It works well for planes as well as birds!

Therefore, the pressure differences of a fluid exerted on an object can move that object. To illustrate Bernoulli's principle, try some of the experiments below.

This activity was developed by the Cosmodôme.

## Mission description

Participants can try out Bernoulli's principle for themselves, using everyday objects! In small groups, they will create hypotheses, conduct experiments, and share their reflections on the observations they made. (See participant handout for experiment instructions.)

### Timeline

Breakdown Duration
Introduction 5 minutes
Experiment 1: Sheet of Paper in the Wind 10 minutes
Experiment 2: Ball Behaviour in a Jet Stream 10 minutes
Experiment 3: Distance Between Two Aluminum Cans 10 minutes
Experiment 4: Balloons in Love 15 minutes
Experiment 5: Roll, Toilet Paper, Roll! 10 minutes
Total 60 minutes

### Objective

By the end of this mission, participants will be able to:

• Understand the theoretical foundations of Bernoulli's principle
• Make connections between the forces that affect the flight of an airplane and the Bernoulli principle
• Develop a hypothesis, conduct an experiment and reach a conclusion

## Mission preparation

### Materials per team (of 3 to 4 people)

• Participant handout (1)
• Hairdryer with nozzle (1)
• Ping-pong ball (1)
• Empty aluminum cans (2)
• Metres of string (2 × 1 metre)
• Plastic stick (broomstick) (1)
• Roll of toilet paper (1)
• Inflatable balloons (party) (2)

### Materials for each team member

• Straw (1)
• Half a sheet of 8.5" × 11" paper

## Mission instructions

1. Participants form teams of three or four people.
2. Using the scientific method, each team performs the five experiments.
3. At the end of each experiment, the participants share their reflections on the observations made. (See participant handout)