Aeronautics Research Mission Directorate 

Changing Pressure

 

Suggested Grades: 5-8 

Time: 45 minutes

Materials

• One straight straw

• One flexible straw

• One piece of paper (3.5 inch x 4

inch) 

• Two empty soda cans

• One cheese puff

Activity Overview

In the following activities, you will see how moving air 

changes the pressure that affects objects. This is known 

as the Bernoulli principle, and is what creates the 

upward force of lift on airplane wings. 

Steps

Paper Tent

1. Fold the paper in half to make a paper tent. 

2. Place the paper tent on a flat surface such as a table or a desk.

3. Position the straw about 2 inches away from the paper tent so that you will be able to 

blow a steady stream of air across the surface of the table or desk and through the tent. 

4. Observe what happens. 

5. Now, blow harder and observe what happens.
You should see the edges of the card pulling together. If not, you may have the end of 

your straw too close to or too far away from the paper tent, or you may not be blowing 

hard enough. 

Magical Soda Cans

1. Place the two empty soda cans parallel to one another and 3⁄4 of an inch apart on a flat 

surface such as a table or desk. 

2. Use a straw to blow between the two cans about 11⁄4 inches above the surface of the table 

or desk. Be sure that the open end of the straw is in front of the cans and not between 

them.

3. Observe what happens. 
The cans should move together when you blow. If not, you may have the cans too far 

apart, the straw may be too close or too far away from the cans, or you may not be 

blowing forcefully enough through the straw. 

Balancing Cheese Puff

1. Bend your straw into an “L”. 

2. Place the long end of the straw in your mouth, with the short end pointing upwards. 

3. Take a deep breath and blow steadily through the straw. 

4. Try to balance the cheese puff in the stream of air coming out of the end of the straw. 

 

5. Now tilt your straw and try to complete the activity. 

6. Observe what happens. 

The cheese puff should stay in the stream of air when the straw is pointed upwards, and 

also hover above the straw when at an angle until a certain point. If not, you may not be 

blowing forcefully enough through the straw, or you may be blowing with too much 

irregularity (The cheese puff may also be an irregular shape.). A steady stream works 

best. One technique to try is to get the cheese puff to spin slightly, which can help with 

any irregularities in its shape.

Background Information 

When we think of fluids, we usually think of a liquid such as water. Air, however, is also 

considered a fluid because it flows and can take on different shapes. As fluids flow (or move) they 

have certain properties that we can observe.
The Bernoulli Principle

A Dutch-born scientist named Daniel Bernoulli claimed that as a fluid moves faster, it produces 

less pressure, and conversely, slower moving fluids produce greater pressure. This idea is known 

as the Bernoulli principle, and is what you saw in the experiments you just conducted. 

In the paper tent experiment, the sides of the card should pull towards one another when you blow 

air between them. The reason for this outcome is that the faster moving air under the card creates 

relatively lower pressure compared to the air over the card, and as a result, the card bends toward 

the table or desk. According to the Bernoulli principle, higher pressure air pushes toward lower 

pressure air. 

In the magic soda can experiment, the two cans move together when air is blown between them. 

The reason for this is that the air blowing through the straw will be faster moving than the air on 

any other side of the cans. Thus, according to the Bernoulli principle, the faster moving air exerts 

lower pressure and the two cans draw toward each other. 

In the balancing cheese puff experiment, the cheese puff balances itself in the steady stream of air 

coming from the short end of the straw. This happens because the air coming out of the straw is 

moving fast, so the faster moving air has less pressure than the slower moving or still air around 

the cheese puff. If the cheese puff starts to move away from the air stream, it experiences pressure 

from the still or slower moving air, which pushes the cheese puff back in place. If, however, the 

straw is tilted, the force produced by the stream of air will no longer be sufficient to keep the 

cheese puff afloat because the force of gravity will then take over.

How does the Bernoulli principle help airplanes fly?

The force that pushes upward on an airplane 

is called lift and is created by the movement 

of air over the wing. Because of the shape of

an airplane’s wing, called an airfoil, the air 

into which the airplane flies is split at the 

wing’s leading edge, passing above and 

below the wing at different speeds so that the

air will reach the same endpoint along the 

trailing edge of the wing at the same time. In 

general, the wing’s upper surface is curved so 

that the air rushing over the top of the wing speeds up and stretches out, which decreases the air 

pressure above the wing. In contrast, the air flowing below the wing moves in a straighter line, 

thus, its speed and pressure remain about the same. Since high pressure always moves toward low 

pressure, the air below the wing pushes upward toward the air above the wing. The wing, in the 

middle, is then lifted by the force of the air perpendicular to the wing. The faster an airplane moves, 

the more lift there is. When the force of lift is greater than the force of gravity, the airplane is able 

to fly. 

Figure 1. The movement of air over an airfoil