What explains the result?
Escaping air pushes backward while the balloon moves forward; this is a simple action–reaction model.
PHYSICAL SCIENCE · GRADES 4–8
Balloon rocket force track
INVESTIGATION QUESTIONHow does balloon size change travel distance?
● ILLUSTRATIVE SCIENCE MODEL
ENGLISH CAPTIONS
Build a straight track. A straight low-friction track helps the balloon move freely.
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Where does this matter?
Rockets, jet engines, and air-powered tools use momentum transfer.
What should you keep in mind?
String slope, balloon shape, leakage, and friction affect the distance.
NEWTON'S THIRD LAW · MOMENTUM · REPEATABLE TEST
Build a
balloon rocket
Thread a straw on a level string, inflate one balloon size, then release it. Compare how far the same balloon-and-straw assembly travels.
STRAIGHT STRING TRACK · SIDE VIEWREADY TO RELEASE
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Medium
STARTDISTANCE MARKS (cm)The balloon is waiting at the start. Choose an inflation level and launch.
AFTER THE LAUNCHES
Explain the motion
Air pushed backward exits the balloon. The balloon is pushed forward in the opposite direction: an action–reaction pair described by Newton's third law. The escaping air also carries momentum. As air leaves, pressure and thrust change, and friction with the string slows the rocket.
TRIAL LOGSmall: not launchedMedium: not launchedLarge: not launched
Where this applies: Jet engines and rockets accelerate by expelling mass in one direction; the vehicle gains momentum in the other. A balloon rocket illustrates the principle, but is not a scale model of a rocket engine.