Before You Start
Get everything you need
🧰 Materials
String or fishing line (at least 10 feet)
Straw (1 per balloon tested)
3 balloons of different sizes
Tape (masking or scotch)
Rocket Race Score Sheet printable
Ruler or tape measure
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⚠️ Safety First!
Always aim the balloon away from faces — let's keep this launch safe!
Always aim the balloon opening away from faces
Keep balloons away from very young children
Make sure string is tied to stable, non-toppling supports
If tape won't stick, try a second layer
What You'll Do
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You're going to build a real working rocket launcher out of a balloon, a straw, and a piece of string — then race balloons of different sizes to see which one flies the farthest!
When you let go of the balloon, air rushes out the back super fast. That escaping air pushes the balloon forward in the opposite direction — the exact same idea that launches real rockets into space!
This is called Newton's Third Law: every push creates an equal push back the other way. You'll test it for yourself by racing small, medium, and large balloons down your string track.
Balloon Rocket Race Track
Follow along carefully
Set Up the String
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Tie your string tightly between two sturdy points (chair backs, doorknobs, or table legs) — stretch it as tight as possible.
Tip: The tighter the string, the faster your rocket will travel!
2
Thread the Straw
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Thread a straw onto the string BEFORE tying the second end.
Tip: Don't forget this step — you can't add the straw after both ends are tied!
3
Blow Up the Balloon
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Blow up a small balloon and pinch the end shut — do NOT tie it.
Tip: Pinch tight with your fingers so no air escapes yet!
4
Tape It to the Straw
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While keeping the balloon pinched, tape it securely to the underside of the straw. Use two pieces of tape for a firm hold.
Tip: Make sure the balloon opening points toward the far end of the string!
5
Aim and Predict
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Slide the straw to one end of the string. Record your prediction: how far will it go?
Tip: Will it reach the other end? Write your guess down first!
6
Release and Record
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Release! Record the result on your Rocket Race Score Sheet. Repeat with a medium balloon and a large balloon.
Tip: Compare all three sizes — which one traveled farthest?
Try It Different Ways
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Little Kids (5-6)
An adult blows up and tapes the balloon while the child holds and releases it. Focus on counting "1, 2, 3, blast off!" and watching it zoom.
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Big Kids (7-8)
Build and tape the balloon to the straw independently, then test and record results for all 3 balloon sizes on the Score Sheet.
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Challenge!
Try tilting the string at an angle, or pointing the balloon opening sideways instead of straight back. Does the rocket still travel the full length?
What's Happening?
🧒 Kid Explanation
When you blow up a balloon and let it go without tying it, all that squished-up air rushes out the back opening as fast as it can. That rushing air pushes against the balloon — and pushes it forward!
It works just like a real rocket! Rockets blast hot gas out the bottom, and that push sends the rocket flying upward into space. Your balloon does the exact same thing, just on a much smaller — and much safer — scale.
🔬 Grown-Up Explanation
This activity is a direct, hands-on demonstration of Newton's Third Law of Motion: for every action, there is an equal and opposite reaction. As air is expelled rapidly from the balloon's opening (the action), an equal and opposite force (the reaction) propels the balloon forward along the string.
This supports NGSS K-PS2-1, investigating how different strengths of pushes affect the motion of an object. The relative size of the balloon affects the amount of compressed air available to be expelled, which directly affects the thrust generated and therefore the distance traveled — a great entry point into discussing force and motion relationships.