Balloon rocket experiment: a 40-minute forces activity, grades 3–5

1. Thread the string through the straw. Tie or tape the ends between two chairs pulled apart, so the string is tight and level.
2. Inflate the balloon, twist the neck and clip it shut. Don't tie it. Tape the balloon to the straw with two pieces of tape.
3. Goggles on. Pull the balloon back to the start, release the clip and watch. Measure the distance from start to where the straw stopped.
4. Explain the forces: air rushes out of the back of the balloon, and the balloon is pushed the opposite way. For every action there is an equal and opposite reaction. Ask: "Which way did the air go? Which way did the balloon go?"
5. Plan a fair test. As a class, list things that might change the distance: balloon size, string angle, straw length, amount of tape. Each team picks one variable to change and keeps everything else the same. Show how to measure balloon size fairly: wrap a string around the widest part and mark it, so every launch is the same size.
6. Each team runs three launches for each setting and records the distances on the board.
7. Debrief: which change made the biggest difference? Did the results match predictions?

Differentiation: for students who need support, give a three-column table drawn on the board (try, distance, notes) and assign roles: launcher, measurer, recorder. For advanced students, calculate the average distance for each setting and make a bar graph. For English learners, post force, push, opposite, distance and variable with arrows showing direction. For students with fine-motor needs, pre-thread straws and pre-cut tape, and offer the measuring or recording role. For students who startle at the noise, give a heads-up countdown before each launch and let them stand farther away.

Quick check: draw a balloon on a string and add two arrows, one for the air and one for the balloon, and label each.

If you try it, tell us which variable gave your class the biggest change in distance.