Elasticity, Simple Harmonic Motion

Abstract

In several places in preceding chapters we have pointed out that when bodies are subject to forces, they change shape, or deform. The general study of the relation between deformations, or strains, and the forces within bodies is called rheology (from a Greek root meaning “flow”). Different kinds of materials may be classified Theologically depending upon the nature of internal forces resulting from different varieties of strain. Commonly materials are divided into fluids and solids. A stationary fluid (which may be either a liquid or a gas depending upon whether or not it can have a free surface) develops internal forces only if its volume has changed, not if its shape has changed. A solid on the other hand, develops internal forces because of changes in shape as well as volume.