PRESSURE
Pressure = force acting normally (or perpendicularly) per unit area
Pressure = [Force / Area (p = F / A = N/ m² = Pa, pascal)] or [density x height x gravity = ρhg (liquid)]
Atmospheric pressure-pressure exerted by air around us, 10⁵ Pa at surface of the earth, decreases with altitude

Pressure in liquid-acts in all directions and increases w/ depth

A simple mercury barometer; instrument for measuring atmospheric pressure, consists of inverted thick-walled glass tube filled w/ mercury placed vertically w/ its open end below surface of mercury in a dish, vertical height of mercury column gives atmospheric pressure in mm Hg (vertical height of tube unchanged if tube is tilted, diameter of tube doesn't affect height)


Gas pressure-measured by a U-tube manometer
Pressure of gas = Atmospheric pressure + height = A + h

average value of barometric height at sea-level = 760 mm Hg = standard atmospheric pressure = 1 atmosphere
pressure = density x height x gravity =13600 x 760/1000 x 9.8=101300 N/m², 760 mm Hg = 101300N/m² = 1 atmosphere
pressure measured in bars, 1 bar = 10⁵N/m², 1 millibar = 10²N/m²
Isobars; lines on weather maps joining places of equal air pressure
Pressure gradient; diff in pressure across 2 regions, diff v. large, pressure gradient high, wind; high > low pressure
Average pressure at sea level = 1016mb
high pressure = 1030mb: calm, dry weather, morning fog, afternoon sun, low pressure = 990mb: stormy wind, cloud, rain
Temperate latitude-vary rapid pressure changes-cyclones and anticyclones

Light
Magnetism
Electrostatic Charging
Electricity
Thermal Physics
Waves & Sound
Radioactivity
Measurements in Physics
Forces
Energy

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