Physical Sciences 2, Fall 2007
Some Introductory Notes about Elasticity
(supplement to the material in the textbook)
Many common materials are soft, squishy, and flexible. We frequently stretch or deform
materials, such as when we repair objects (a building, a patient, etc.) or when we
manipulate living systems: forces produce deformations such as when we bend objects
and break things. The coatings of many surfaces – including our skin, deformed balloons,
and clothing – are wrinkled and stretched. To understand these observations, and to
quantify them, we begin with Hooke’s law for the
a spring, and modify it slightly to describe the
in a material. We will see
that we can then learn about and quantify how, and by how much, mechanical forces
deform objects, whether they are steel structures, your bones, tissues or cells. Earlier in
the course we referred to the idea that
everything is a spring
; the characterization of the
elastic response of materials is a wonderful example of this analogy.
College Edition 1968):
Adjective: 1. Having the property of immediately returning to its original size, shape, or
position after being stretched, squeezed, flexed, expanded, etc; flexible, springy. 2.
having the ability to recover easily from dejection, fatigue, etc. 3. readily changed or
changing to suit circumstances; adaptable. Noun: 1. a loosely woven fabric made flexible
by strands of rubber or a rubberlike synthetic running through it. 2. a band, garter, etc. of
this material; 3. a rubber band.