In many applications, the desired mechanical properties are required at a minimum weight. To do this, we define “specific” properties such as specific stiffness or specific yield strength. Specific properties allow the lightest material required to meet property requirements to be identified. This is discussed in more detail in property comparisons.

As an example, consider an application where we want to achieve a given strength at a minimum weight. This is a common requirement in transportation.

Light, stiff, strong components are required for cars and aeroplanes

The weight of a component will depend on the material used and the volume of the component. We are interested in the dependence of the weight on the material alone, and so eliminate the component volume by comparing density. Density is a material property.

Density is defined as mass per unit volume (units kg m⁻³).

Which one of the following statements is most correct:

For a strong, lightweight component, we require a material with: