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GCSE Physics · key term
The force per unit area exerted on a surface by air molecules colliding with it.
Used by AQA, Edexcel and OCR
Specification 4.5.5.2 · Paper 2
Revise: Atmospheric pressureTogether, the collisions produce atmospheric pressure: force per unit area. The air can therefore press on surfaces facing in different directions, not just on surfaces beneath it.
Specification 15.7P, 15.8P · Paper 2
The normal force exerted per unit area by air particles colliding with a surface.
Revise: Atmospheric PressureThe combined force from enormous numbers of collisions produces atmospheric pressure. Pressure is force per unit area, and the force acts at right angles to a surface. Because air particles move in every direction, atmospheric pressure acts in every direction rather than only downwards.
The pressure exerted by the air in Earth's atmosphere.
Specification P1.3f, P1.3g · Paper 1 (Foundation), Paper 3 (Higher)
The pressure exerted by the atmosphere on surfaces within it.
Revise: Model of Earth's atmosphereAir molecules move in every direction, so atmospheric pressure acts on surfaces of every orientation. For example, the atmosphere pushes on the top, sides and underside of an object. Each pressure force acts at right angles to the particular surface.
The force exerted by the atmosphere per unit area of a surface.
Paper 1, Paper 2
The pressure exerted by the air surrounding Earth.
Revise: Atmospheric and Liquid PressureAt a particular height, atmospheric pressure acts in all directions.
For a height question, link fewer air molecules above the surface to lower air density and fewer collisions with that surface, then state that atmospheric pressure is lower.
Do not claim that atmospheric pressure falls because gravity disappears. Gravity still acts at mountain and aircraft heights; there is simply less overlying air.
When comparing two heights, state explicitly that atmospheric pressure is greater at the lower height and support the comparison using the simple atmosphere model.
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