Forces, Deformation, Springs & Pressure

Vocabulary flashcards covering key terms about forces, deformation, Hooke’s law, springs and pressure from the lecture notes.

Deformation

A change in the size or shape of an object caused by applied forces (stretching, squashing, bending or twisting).

Elastic Deformation

Temporary deformation; the object returns to its original shape once the force is removed.

Inelastic (Plastic) Deformation

Permanent deformation; the object does not return to its original shape after the force is removed.

Compression

A force that squashes or shortens an object.

Extension

The increase in length of a spring or material when a load is applied (stretched length − original length).

Load

The force applied to stretch, compress, bend or twist an object (often measured in newtons).

Hooke’s Law

States that the extension of a spring is proportional to the load applied, provided the limit of proportionality is not exceeded (F = kx).

Limit of Proportionality

The point beyond which extension is no longer proportional to load and the spring begins to suffer permanent damage.

Spring Constant (k)

A measure of a spring’s stiffness; defined as the force per unit extension (k = F/x).

Stiffness

The resistance of an object or material to deformation; greater stiffness means a larger spring constant.

Elastic Cord

A stretchable cord that obeys Hooke’s law up to its limit of proportionality before permanent deformation occurs.

Rubber Band Behaviour

Exhibits a non-linear (S-shaped) load-extension graph; extension not exactly proportional to load and shows hysteresis when unloaded.

Bungee Cord

A highly elastic rope that stretches to absorb energy, then recoils to slow and rebound a jumper safely.

Robert Hooke

17th-century British scientist who discovered the proportional relationship between force and extension in springs.

Pascal (Pa)

The SI unit of pressure, equal to one newton per square metre (1 N/m²).

Pressure (p)

Force per unit area acting on a surface (p = F/A).

Density (ρ)

Mass per unit volume of a substance; affects pressure in fluids and is measured in kg/m³.

Depth (h)

Vertical distance below the surface of a fluid; deeper depth increases fluid pressure.

Fluid Pressure Formula

Change in pressure with depth: Δp = ρ g Δh (density × gravitational acceleration × depth).

Gravitational Acceleration (g)

Acceleration due to Earth’s gravity, approximately 9.8 m/s²; used in pressure and force calculations.

Load–Extension Graph

A plot showing how a spring’s extension varies with applied load; linear region obeys Hooke’s law, curved region shows damage.

Elastic Behaviour

The ability of a material to store energy when deformed and release it when returning to its original shape.

Inelastic Damage

Permanent change in length or shape after exceeding the elastic limit, observed as residual extension.

Foam Rubber

A highly elastic, easily deformed material that returns to its original shape when forces are removed; useful for deformation demonstrations.

Stiletto Heel Example

Illustrates how a small area with a moderate force produces very high pressure capable of damaging floors.