We’re going to experiment with Newton’s Third law by blowing up balloons and letting them rocket, race, and zoom all over the place. When you first blow up a balloon, you’re pressurizing the inside of the balloon by adding more air (from your lungs) into the balloon. Because the balloon is made of stretchy rubber (like a rubber band), the balloon wants to snap back into the smallest shape possible as soon as it gets the chance (which usually happens when the air escapes through the nozzle area). And you know what happens next – the air inside the balloon flows in one direction while the balloon zips off in the other.

Question: why does the balloon race all over the room? The answer is because of something called ‘thrust vectoring’, which means you can change the course of the balloon by angling the nozzle around. Think of the kick you’d feel if you tried to angle around a fire hose operating at full blast. That kick is what propels balloons and fighter aircraft into their aerobatic tricks.

We’re going to perform several experiments here, each time watching what’s happening so you get the feel for the Third Law. You will need to find:

  • balloons
  • string
  • wood skewer
  • two straws
  • four caps (like the tops of milk jugs, film canisters, or anything else round and plastic about the size of a quarter)
  • wooden clothespin
  • a piece of stiff cardboard (or four popsicle sticks)
  • hot glue gun

First, let’s experiment with the balloon. Here’s what you can do:

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33 Responses to “Balloon Racers”

  1. What do you have a question about, specifically? 🙂

  2. Tracy Davis says:

    haw do you do that
    Judah 8.

  3. Lisa Stoner says:

    So cool!!! Best science project ever!!!

  4. Ching-Yu Hsu says:


  5. Debbie Aslinger says:

    I adjusted the wheels so now it rolls perfectly when I push it very gently…but the balloon still won’t power it! I checked the airflow from the balloon and it’s fine, too! Any ideas on what might be wrong with it?

    -Lucy Aslinger-

  6. You’ll want to be sure the car rolls easily first… just a gentle push should get it moving. Then when you add the balloon, make sure that it exhales in a straight line directly behind the car so all the forces gets translated to the right direction.

  7. Debbie Aslinger says:

    I can’t get the car to work right. Air comes from the balloon, and when I push it it rolls just fine. But when I attach the balloon and don’t push it, the air just leaks out of the balloon and the car stays put. Any tips?

    -Lucy Aslinger-

  8. Of course! Adjust it however you like!

  9. Laura Hoggard says:

    That looks like a lot of fun if we can get it to work.Is it pliable, meaning can we mess with it? Because I think I might experiment and see what works.

  10. Sure – let me know how it goes! And send me a picture…

  11. Natalie Roth-Corti says:

    For the length contest, can i use wings instead of putting the rocket on a string?

  12. What exactly happens? Be very specific… what about it didn’t work?

  13. I made it 3 times! All of them didn’t work. The only difference was a smaller clothespin. Everything else I followed exactly! I don’t know what’s wrong with it?..

  14. It doesn’t take much inflation to make this one work. You can try sticking a piece of tape to help hold your balloon in place when you are inflating it between the balloon and cup, or try a larger cup or smaller balloon. Let me know how it goes.

  15. Emily Crawford says:

    I’m trying to make the multi-stage rocket, but I’m having trouble with the part where you stick the end of the big balloon through the cup and then inflate the long balloon inside the cup. Somehow the long balloon inflates mostly OUTSIDE the cup, leaving plenty of room for the first balloon to deflate. 🙁 Do you have any suggestions for making it work?

    -Mary Crawford (age 12)

  16. Lisa West says:

    Kids strung line between their beds and are using the balloon racers as messaging system. 🙂

  17. Vicki Jensen says:

    Why does the balloon spin instead of going straight up the string?

  18. Hmmm… you need to be sure that the straw slides freely along your line, or the friction will be too great for the balloon to overcome as it deflates. Try sewing thread?

  19. Lorelei Grecian says:

    The one where you tape the string to the wall and take the clothespin off it didn’t work. Mabey its because we used ribbon instead of fishing wire? I think it was the balloon because it didn’t blow up that much and didn’t go very far. 🙁

    Raena 🙂

  20. There are two videos on this page: Multi-Stage Balloon Rocket and the Balloon Racecar. Is that what you are referring to?

  21. Caroline Wood says:

    I don’t see the video. Could you give me the link?

  22. Karen Cossey says:

    We got our balloon racer to work in the end – we had trouble even with the ideas of putting a piece of straw in the blowing end of the balloon. Then we tried the casing/body of a pen in the end of the balloon and the racer took off! Great!

  23. We were actually just talking about the travel schedule for 2012 and 2013… this year, we took on too many private events, and my entire schedule booked up so quickly that next time we’re planning to leave a little more room for public events, like we did in 2007-2009 (when we were in Florida doing live camps and talks at FPEA).

    I promise to let you know about the next set of live shows – you really don’t want to miss those, especially the BIG ones – they are my favorite! It’s like a combination of a rock concert, chemistry magic show, rocket launch, and laser show all rolled into one unforgettable weekend of learning!

  24. Jeanette Roberts says:

    This experiment was GREAT but we couldn’t get it to work at first. The trick is to put a small pice of a straw in the blowing part of the balloon making an air hole so the air can escape. And I also highly recommend the Sling shot rocket and the Blow gun rocket. : – ) : – )

    P.S. When are you coming to Florida?

  25. Ok – so the new players we are installing work better for you -yea! We’re slowing updating the site over the next several weeks with this type of player, so stay tuned. You won’t notice anything physically different, but you WILL notice that the videos load faster and play more smoothly.

    In the meantime, try this for any others you have trouble with: hit PLAY then hit PAUSE and wait for it to download completely, then hit PLAY again.

  26. TRACY RAYNOR says:

    Are there other things you can use rather than coffee stirrers?
    Question made by the wonderful Skylar!

  27. Darla Shannon says:

    it plays through to the end, thanks!

  28. Ok, I’ve had a second player uploaded for you for the multi-stage balloon rocket. Can you test this player for me? It’s the second one down – the one with the image. Tell me exactly what happens and when so we can figure this out for you.

  29. Darla Shannon says:

    i have the latest version of flash, and have DSL. i primarily use windows xp media center, but i have also tried it on windows 7 ultimate, and with multipul browsers, it still does the same thing

  30. I think you’ve got an issue with your internet and/or your flash player. You’ll want to download the latest version from Adobe Flash. Once you get this fixed on your end, you’ll be able to play the videos all the way through, including the other ones you commented on as well.

    Both videos play all the way to the end over here – what happens if you try a different computer?

  31. Darla Shannon says:

    the first video starts over at 21 seconds and the second at 26 seconds, please fix it today

  32. Holly Loussaert says:

    Remember to use popsicle sticks and not tongue depressors. The larger stick seems to be too heavy to allow the racer to race. We tried the bigger stick at first but went to the popsicle stick and the racer just took off like a shot in the dark. 🙂 Very impressive.

  33. Aimee Williamson says:

    Loved it! Last year we bought balloon racers, commercially made, that didn’t work, but these homemade ones are light enough to work well! For a variation, we used a bread bag tab hot-glued on the end instead of a clothespin glued to the top and that worked well too…and was free! See below:

    Balloon Racer