Property

Definition

Strength

How much force is needed to break something.  Not always a fair comparison.  Something that is thick will be stronger than a thin section.  A fairer test is the breaking stress.

Breaking Stress

Breaking stress = breaking force

                                area

Force is applied at 90 ^o to the area.

Stiffness

How difficult it is to change the shape of the object.  If we load wires of the same length and diameter with the same tension, the stiffest is the one that stretches the least.

Brittle

Stiff, but not strong

Elastic

Ability of a material to regain its original shape after it is distorted.

Plastic

A material that does NOT regain its original shape after it is distorted.