Answer» Stress: In mechanics, stress is defined as force applied per unit area. It is given byσ = F/Awhere, σ is the stress appliedF is the force appliedA is the area of force applicationStress is expressed as N/M2.Strain: The strain is the amount of deformation experienced by the body in the direction of force applied, divided by initial dimensions of the body. The relation for deformation in terms of length of a solid is given below.ϵ = δl/ Lwhere, ϵ is the strain due to stress appliedδl is the change in lengthL is the original length of the material.