In materials context, what does the modulus of elasticity represent?

• A. It represents the density of the material.
• B. It represents the slope of the stress-strain curve.
• C. It represents the yield strength.
• D. It represents the ultimate strength.

Answer: (B)

Modulus of elasticity measures stiffness, describing how much a material elastically deforms under load. It is defined as the ratio of stress to strain in the elastic region, which means it equals the slope of the stress-strain curve during the initial linear portion. This property tells you how stiff the material is, not how strong it is. Yield strength and ultimate strength relate to when and how a material yields or fails, while density is unrelated to deformation under load.