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Little Labs: Balloon Rocket!

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Watching a rocket propel itself into space is one of the most exciting things to see. But did you ever wonder what makes it go?

Well, yes, fuel of course. But fuel is only pushing against the ground. Why does the rocket move in the opposite direction, up?

You might have heard this famous phrase before:

"For every action, there is an equal and opposite reaction."

That’s from Isaac Newton’s Third Law of Motion. This law helps us to predict how things will move.

Wanna test this yourself? Let’s make a balloon rocket!


  • Yard stick/measuring tape
  • String
  • Balloon
  • Masking tape
  • Straight drinking straw
  • Data table on paper that looks like this:



    Distance Traveled


You may also want a friend or parent to help as your lab partner!


  1. Blow up a balloon as big as you can. Pinch it off, but don't tie it closed.
  2. Wrap a piece of string around the middle of the balloon. (Your lab partner can hold the balloon closed while you wrap the string around it.)
  3. Measure the length of the piece of string. This is the circumference of balloon – or how big around the balloon is. Enter this length in the data table.
  4. Thread a long piece of string (10-15 feet) through the drinking straw.
  5. Attach the straw to the balloon with two pieces of masking tape.
  6. Attach one end of the string to a doorknob, a wall, or have your lab partner hold it.
  7. Pull the other end of the string tight and make sure it is level. Move the inflated balloon toward this end of the string.
  8. You're ready for launch! Let the balloon go and watch it fly like a rocket!
  9. Measure how far it went with your yard stick or measuring tape. Record the distance in your table.
  10. Now change the size of the balloon by blowing it up less, say half full, and repeat the steps. Try again with the balloon about a quarter full. Record your results in the table.


What's going on?
When you let go of the balloon, the air inside rushed out creating a force called thrust. Since the balloon is so light, the air is enough to propel (or push) the balloon forward.

For every action, there is an equal and opposite reaction:
Physicists call the air that came out of the balloon the ‘action force’ and the force that pushed the balloon forward the ‘reaction force’. When an action force goes in one direction, the reaction force goes in the opposite direction. The bigger the action force, the bigger the reaction force. This is why the balloon with most air in it went the farthest!

With real rockets, thrust comes from the force of burning rocket fuel as it blasts from the rockets engine. As the engines blast down, the rocket goes up! Just as Newton predicted: “For every action there is an equal and opposite reaction.” In other words, when you push on something, it pushes back on you just as hard!


Let us know what you did. Share your photos and results with us on Facebook, Twitter, or send us an email to We love getting your messages!

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Chelsea Schuyler
Chelsea Schuyler