Why does the roof of a house sometimes get lifted off during a storm even though the wind blows sideways, not up?
Fast-moving air over the roof lowers the pressure there (Bernoulli's principle: faster flow → lower pressure).
Fast-moving air over the roof lowers the pressure there (Bernoulli's principle: faster flow → lower pressure). The air inside the house is still, so it stays at higher pressure. That pressure difference pushes the roof upward. The same physics gives an aeroplane wing its lift and makes two passing trucks get sucked toward each other.
Key point
Fast air = low pressure; the still, high-pressure air underneath pushes up.
Common mistake
assuming the wind must blow upward to lift the roof.
Memory tip
wherever a fluid speeds up, its pressure falls — that's lift.
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