Unit 8: Fluids

Fluid

A substance (liquid or gas) that flows and takes the shape of its container.

Density (ρ)

Mass per unit volume, calculated as ρ = m/V.

Viscosity

A measure of a fluid’s resistance to flow.

Compressibility

How much a fluid's volume changes under pressure.

Pressure (P)

Force per unit area, measured in pascals (Pa).

Hydrostatic Pressure

Pressure exerted by a fluid at rest, given by P = ρgh.

Gauge Pressure

Pressure above atmospheric pressure.

Absolute Pressure

Gauge pressure plus atmospheric pressure.

Buoyancy

The upward force a fluid exerts on a submerged object.

Archimedes’ Principle

The buoyant force is equal to the weight of the displaced fluid.

Pascal’s Principle

Pressure applied to a confined fluid is transmitted undiminished throughout.

Hydraulic Systems

Systems that use incompressible fluids for force multiplication.

Laminar Flow

Smooth, orderly flow of fluids in layers.

Turbulent Flow

Chaotic, irregular flow of fluids.

Continuity Equation

Expresses the conservation of mass for fluid flow: ρ1A1v1 = ρ2A2v2.

Bernoulli’s Principle

When velocity increases, pressure decreases; described by P + 1/2pv² + pgh = constant.

Reynolds Number

A dimensionless number used to predict flow type (laminar vs. turbulent).

Ideal Gas Law

Relates pressure, volume, temperature, and number of moles in a gas: PV = nRT.