Materials Definitions

Definitions for Chapter 4 content.

Archimedes’ Principle

When a body is fully or partially submerged in a fluid, it experiences an upthrust equal to the weight of the fluid it has displaced.

Breaking Stress

The maximum stress a material can withstand without fracturing.

Brittle

A material that fractures without plastic deformation first.

Density

Mass per unit volume, with units kgm-3.

Ductile

A material that can withstand large plastic deformation without breaking, allowing them to be stretched into long wires.

Elastic Deformation

When a material can return to its original shape after stress without a permanent change.

Elastic Limit

The maximum stress that can be applied to an object without plastic deformation.

Hooke’s Law

The extension of an object is directly proportional to the force being applied to it.

Laminar Flow

A state of flow where layers of fluid move together in parallel with little or no mixing between layers.

Limit of Proportionality

The point where stress on an object is so great that Hooke’s law no longer applies.

Plastic Deformation

When a material is permanently deformed after an applied stress due to atomic movements.

Stoke’s Law

The force of viscosity acting on a spherical body moving through a fluid is proportional to its radius, velocity, and fluid’s viscosity.

Tensile Strain

The extension of an object divided by its original length.

Tensile Stress

The internal resistance of an object against a deforming force; force applied per unit cross-sectional area.

Turbulent Flow

A state of flow where layers of fluid mix together unpredictably, causing chaos.

Viscosity

A quantity measuring the internal friction of a fluid, acting to reduce its flow; temperature dependent.

Upthrust

The force felt against the weight of an object when submerged in a fluid, equal to the weight of the displaced fluid.

Yield Point

The point on a force-extension graph at which a material begins to extend rapidly without additional stress.

Young’s Modulus

The ratio of stress to strain of an object; a measure of how stiff a material is.