How to play Storm and Wing
- Choose a test and read the speeds, the mass, and the area on the card.
- Faster air has lower pressure: the drop is ½·ρ·v², so faster air over the top than under it leaves a pressure difference.
- That difference acts on the whole area: F = ½·ρ·(v_over² − v_under²)·A. Type your prediction and press Start.
- Watch the bars: a roof, a plane, or a strip lifts the moment the lift reaches its weight.
How can moving air lift a roof?
Bernoulli's principle works in air too: where air moves faster, its pressure is lower, by ½·ρ·v² compared with still air. Air is light, about 1.2 kg per cubic metre, so the drop seems small: 540 Pa for a 30 m/s storm, about half a percent of the air's pressure. But it acts on every square metre. On a 100 m² roof, with still air inside the house pushing up at full pressure, that's 54 kN, enough to lift a heavy roof clean off. A wing works the same way: shaped and tilted so that air flows faster over the top than underneath, it feels a pressure difference ½·ρ·(v_over² − v_under²) over its whole area, and the faster the plane goes, the bigger it gets, growing with v². That's why planes need a runway to reach take-off speed. Blow over a strip of paper and it rises for the same reason.
A focused learning model
Air is 1.2 kg/m³ and doesn't compress at these speeds; the air under a roof or a strip is still, and the pressure difference acts evenly on the whole area. The wind, the plane, or your breath speeds up steadily for 2 s; something that lifts does so the moment F = ½·ρ·(v_over² − v_under²)·A reaches its weight (within 0.15% still lifts), and is drawn rising for 1 s. Real wings also push air downward, which this model leaves out. Nothing is to scale. A force is right within 2%; a speed must lift with at most 2% to spare. g = 9.8 m/s². Plays in real time.