Water Bottle Rocket
Pressurised air and water blast a soda bottle skyward — a vivid lesson in thrust and Newton's third law.
Start building ↓The build
Add fins
Tape three or four fins around the bottle for stability.
Fill with water
Add water to about one-third full.
Seal & pressurise
Push in the cork-and-needle and pump air in outdoors.
Launch
Release — water jets down and the rocket leaps up.
Compressed air forces water out the nozzle; the downward water jet pushes the rocket up with an equal and opposite reaction force.
A closer look
Thrust comes from expelling mass (water) quickly. More pressure and the right water amount maximise momentum transfer and altitude.
Variables to test
- 1 Vary the water level and measure peak height.
- 2 Change fin size — how does it affect a straight flight?
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