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Why a spoon jumps toward the faucet: the effect that keeps planes up
💡 Fast-moving fluids cling to and follow curved surfaces because they create a low-pressure zone that pulls the flow — and nearby objects — inward.
Hold the back of a spoon near a running tap and it doesn't get pushed away — it gets pulled into the stream. This is the Coandă effect: a moving fluid (liquid or gas) tends to cling to a nearby curved surface and follow it, rather than flying off in a straight line. It's named after Romanian engineer Henri Coandă, who noticed hot exhaust hugging the body of an early aircraft he built in 1910.
The reason comes down to pressure. As the water speeds up around the spoon's curve, it drags surrounding air along and thins it out, creating a slightly lower-pressure zone hugging the surface. The higher pressure on the other side pushes the stream against the spoon — and, by Newton's third law, pushes the spoon toward the stream.
This isn't just a kitchen trick. The Coandă effect helps explain how airplane wings and flaps steer airflow to generate lift, how hand dryers and bladeless fans sling air in a smooth sheet, and how race cars manage the air rushing under and over their bodywork. The same clinging behavior even shapes how mixing taps blend water.