Glossary
Atmospheric Pressure
Atmospheric pressure is the pressure exerted by the weight of the air column in the Earth's atmosphere above a given point.
Example:
At high altitudes, the atmospheric pressure is lower, which is why water boils at a lower temperature.
Bernoulli Effect
The Bernoulli Effect describes the inverse relationship between the speed of a fluid and the pressure it exerts on its surroundings; faster fluid flow corresponds to lower pressure.
Example:
The curved shape of an airplane wing causes air to flow faster over the top surface, creating lower pressure above the wing and generating lift, a direct application of the Bernoulli Effect.
Dynamic Pressure
Dynamic pressure is the component of fluid pressure that arises from the fluid's motion, proportional to the fluid's density and the square of its velocity.
Example:
As wind rushes over a building, the moving air creates dynamic pressure on the surfaces it hits, which can be significant during a hurricane.
Gauge Pressure
Gauge pressure is the pressure measured relative to the ambient atmospheric pressure. It represents the pressure exerted solely by the fluid above the measurement point.
Example:
The pressure displayed on a car tire gauge is the gauge pressure, indicating how much higher the tire's internal pressure is compared to the outside air.
Hydrostatic Pressure
This is the pressure exerted by a fluid at rest due to the weight of the fluid above a certain depth. It depends on the fluid's density, gravity, and depth.
Example:
A deep-sea diver experiences immense hydrostatic pressure because of the enormous column of water pushing down from above.
Pascal's Principle
Pascal's Principle states that a pressure change at any point in a confined incompressible fluid is transmitted equally to every other point in the fluid and to the walls of the container.
Example:
A hydraulic jack uses Pascal's Principle to lift heavy cars: a small force applied to a small piston creates a much larger force on a larger piston.
Pressure
Pressure is a scalar quantity defined as the ratio of force applied perpendicular to a surface to the area over which the force is distributed.
Example:
When you push a thumbtack into a board, the small tip of the tack creates a very high pressure on the wood, allowing it to penetrate easily.
Scalar
A scalar is a physical quantity that has magnitude but no direction.
Example:
Temperature, mass, and volume are all scalar quantities, unlike force or velocity which are vectors.
Total (Absolute) Pressure
The total pressure at a given point in a fluid is the sum of the gauge pressure (pressure due to the fluid itself) and the atmospheric pressure acting on the fluid's surface.
Example:
When measuring the pressure inside a sealed tire, the reading on the gauge is the gauge pressure, but the actual total (absolute) pressure inside is that reading plus the surrounding atmospheric pressure.