This year in Science, we are studying all things that fly. So what factors are involved in flight? We are looking at birds first, and the shape of the wing is important to create lift. The top of the wing is curved whereas the underside of the wing is more straight. Because of this, the air traveling over the top of the wing has to move fast in order to meet the air moving under the wing. The fast moving air creates less pressure, while the air moving beneath the wing maintains its speed (which is slower) and maintains its pressure. The result is that there is less pressure pushing down on the wing and more pressure pushing up from beneath the wing. This creates lift, which keeps our feathered friends airborne.
Now let’s demonstrate how this works.
Air Pressure Experiment 1
- 2 toilet paper tubes (spaced 1 inch apart)
- 1 straw
Hypothesis: Ask your child to predict what will happen when they blow air through the straw in between the two TP tubes. (The most common thought is that the tubes will roll away from one another, because when we blow on things they move away.)
- Place the two tubes side by side lengthwise, so that the sides are touching each other.
- Now space the tubes one inch apart.
- Get down level with the table and hold the straw directly in front of the tubes centered in the middle of the empty space between them.
- Blow through the straw, strongly so to create fast moving wind
Results: What happened? The tubes should have moved toward one another, smacking together!
Conclusion: Why did the tubes move toward each other and not roll away? Air pressure! The wind you blew through the straw moved quickly down the center of the tubes. Whereas, the air on the outside of the tubes remained the same and was slower moving in comparison. This created a situation where the air between the tubes placed less pressure on the respective sides of each tube; and the air on the outside of the tubes, moving slower, applied more pressure. The higher pressure won, pushing the tubes together. Pretty neat!
Need further proof? Try this next experiment.
Air Pressure Experiment 2
- 2 balloons
Hypothesis: What do you think will happen when we blow between two suspended balloons? Your budding scientist may now intellectually deduct that the balloons will be pushed together. And He/she would be right! (If he/she thinks they will be pushed away, that’s fine. That’s why we experiment and explore😉)
- Blow up 2 balloons to be the same size.
- Tie a long piece of string to the end of each balloon.
- Find a doorway and tape the string to the top of the doorway so that the balloons are hanging 3 inches apart. The balloons need to hang down far enough so that your mouth is level with the middle of the balloons.
- Take a deep breath and blow across the center of the space between the two balloons.
Results: Did the balloons move toward each other and bump together? They should have.🙂
Conclusion: Once again you have created fast moving air with less pressure between the two objects. The air pressure on the opposite sides of the balloons was higher since the air was moving at a slower pace. Thereby, pushing the balloons into the area with less pressure bringing them together.