Bernoulli, You're Such a Wind Bag!




About: The name Cat’s Science Club comes from my daughter Aly, whom I call Aly Cat. She inspired me to take my love of science, and the fun I have with my students, to as many people as I can. Both my daughters hel...

With just one breath you can fill up a 6 ft bag of air. Way to go wind bag! Challenge friends and coworkers to see how many breaths it takes them to fill up a bag with air.

Step 1: Materials

Materials for this are

Diaper Genie Refills


Step 2: Cut and Tie

Open the diaper genie refill and pull out 6 ft. It does not have to be exact.

Cut the 6 ft length of diaper genie so you have a long bag. Both ends are open.

Tie one end of the bag.

You will now have a long tube bag.

Step 3: Challenge a Friend

Challenge a friend to blow up the bag. Keep count of how many breaths it takes them.

Step 4: Your Turn

Explain to your friend that you can blow up the bag with one breath! Yeah one breath.

Hold the bag opening 9 to 10 inches away from your mouth. Have your friend hold the tied end of the bag.

Blow directly into the bag (still 9-10 inches away) as hard as possible.

As fast as possible, close up the bag to prevent any air from escaping.

Enjoy the confused looks as you stand next to your inflated bag!

Step 5: How?

What just happened? How did that work?

Using Bernoulli's Principle we are able to inflate the bag.

As you are blowing air into the bag more air in the room rushes into replace the air that was between you and the bag. Remember that 9 to 10 inches? The fast moving air from you created an area of low pressure, making the air in the room an area of high pressure. So you not only filled the bag with your air from your lungs but also with the air from the room.

"Bernoulli's Principle - the statement that an increase in the speed of a fluid produces a decrease in pressure and a decrease in the speed produces an increase in pressure" according to the Webster Dictionary.

We don't have to make it so complex to understand. The air flowing faster has low pressure and the slower air has a high pressure.

Step 6: Teacher

As a teacher I used this in my classes when I taught 6th grade science and also when I taught 8th grade. Explaining Bernoulli's Principle was a logical step to learning about Newton and building our rockets. Let's learn to fly (using Bernoulli's Principle) before we shoot for the moon (Newton's Laws of Motion).

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    10 Discussions

    Jason S1

    4 weeks ago

    This is great. One of my favorite things I learned about in school.

    1 reply

    4 weeks ago

    Great instable, here is a video I found

    1 reply

    4 weeks ago

    In my classes, I just used a couple of books and a piece of paper. Put the books on a desk about 2 inches across and lay the paper across the gap. Blow through the opening, the paper will suck down into the gap. It's too simply a process to use your example in class.

    1 reply

    4 weeks ago on Step 6

    Very nice! And don't forget how to remove a cork from a wine bottle with a plastic bag!

    1 reply

    5 weeks ago

    Thanks for sharing another fun way to demo science principles. Love that you used this to build up to rockets. :)

    1 reply

    Thanks! The kids always get a kick out of doing these with their own bags. Sometimes it is a demo, sometimes each kid gets their own, all depends on funds. Great fun either way.