WAEC Physics 2018 Paper

Concept:Elastic modulus quantifies the stiffness of a material by measuring how much stress produces a given strain.Explanation:When a force is applied on a body, it causes deformation.The applied force per unit area is called stress.The resulting fractional change in dimension is called strain.Elastic modulus is defined as the ratio of stress to strain.Mathematically, it is written as:$$\text{Elastic modulus} = \frac{\text{stress}}{\text{strain}}$$The unit of stress is $\mathrm{N/m^2}$ and strain is dimensionless, so the modulus has units of pressure.Thus, the general definition matches option A.Answer:A. $\frac{\text{stress}}{\text{strain}}$