This is the first in a series of problems regarding mechanics of materials, in particular, material properties drawn from stress-strain responses. A simplified typical stress-strain response is illustrated below (figure from here):

The yield stress is the pressure required to start deformation of the material being tested. The yield point is the point along the response indicated by the yield stress (vertical axis) and the yield strain (horizontal axis). The response of the material up to this point is elastic, meaning that all deformation is reversible. The elastic modulus (also known as modulus of elasticity or Young's modulus) is the slope of this line. Write a function to calculate the elastic modulus for a material, provided the elastic strain and yield stress (yield point).

Next problem: 2 - resilience.