# Interpretation of Hooke's Law

Unfortunately, both descriptions are misleading because both describe the relationship as a one-way cause-and-effect relationship. The correct way to describe it is

the stress is proportional to the strain

It doesn’t matter if the stress is given and the strain is obtained by Hooke’s law or if the strain is given and the stress is obtained by Hooke’s law. Either way they are proportional to each other.

Unfortunately, whether it is Newton’s laws, Ohm’s law, Hooke’s law, or Maxwell’s equations, the tendency to verbally express such equations in cause-and-effect language is fairly strong and common in many introductory physics courses. It is almost universally inappropriate. A real cause-and-effect relationship is given by an equation of the form $$f(t)=g(t-\Delta t)$$ In this equation $$g$$ is the cause and $$f$$ is the effect and $$0<\Delta t$$ so that the cause always precedes the effect. In an expression like Hooke’s law both stress and strain are happening at the same time and causes happen before effects. It is a simple proportionality, not a cause-and-effect relationship.