Based on a steam-driven toy developed by Hero of Alexandria around 150 BC, this is perfect for a fascinating demonstration of jet propulsion. Our version consists of a small Erlenmeyer flask with a rubber stopper. Two small tubes with tangentially oriented jets extend from the stopper. A collar around the neck lets you hang it above a burner. When water is boiled in the flask, the steam escapes through the jets, causing the flask to spin.
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