Forces & Pressure
Pressure in solids, liquids and gases
Forces and Pressure
Pressure is force per unit area: P = F/A (measured in pascals, Pa). A smaller area means more pressure for the same force. Pressure exists in solids, liquids, and gases.
Example
Pressure Calculations
A person weighing 600 N stands on one foot (area 0.02 m2): P = 600/0.02 = 30 000 Pa. On two feet (area 0.04 m2): P = 600/0.04 = 15 000 Pa — half the pressure! This explains why high heels sink into soft ground.
Note
Key Point
Atmospheric pressure at sea level is about 101 325 Pa. Hydraulic systems use liquid pressure to multiply force. Pressure in a liquid acts equally in all directions (Pascal's principle).
Key Vocabulary
PressureForce per unit area, measured in pascals (Pa)
Pascal (Pa)The SI unit of pressure, equal to one newton per square metre
Atmospheric pressureThe pressure exerted by the weight of the air above a surface
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