Fluid Mechanics B. Pressure Key Concepts Pressure is the force acting perpendicular to a given surface area. Pressure is a scalar quantity, acting in all directions.
Meteorologists express pressure in millibars.
Atmospheric pressure decreases at higher elevations. Standard atmospheric pressure will support a column of mercury 760 mm high. This can be expressed as a pressure of 760 mm Hg, or 760 Torr. A barometer is used to measure atmospheric pressure. The pressure is independent of the total volume or the shape of the container.