Objectives

• Determine the relation between force and extension of a spring and a rubber band

Introduction

A number of physical systems exhibit a linear restoring force when displaced from their equilibrium position. This is described by the relation;

F = -ks    Hooke's Law

            F is the restoring force of the system
            k is a proportionality constant often referred to as the spring constant
            s is the displacement from equilibrium position

Notice this relation is linear (having the appearance of y=mx+b where m=slope and b=0). Applying twice the force will double the displacement. Larger values of k, the spring constant, represent stiffer systems that are harder to stretch.

Hooke's law describes a spring over a limited range of displacements (the relation will not hold if a spring is stretched too far). In this lab you will also consider how well it holds for rubber bands.

References

• Hooke's law and molecular forces
• Rubber bands