An elastic object, such
as a spring, is made of a substance that keeps to a particular shape
without the influence of outside forces. When a force is applied,
as when we stretch or compress a spring, the elastic object exerts
an opposing force. When the outside force is released, the elastic
object regains its original shape. Springs, rubber bands, guitar
strings, balloons, and the air trapped in a shock absorber are all
examples of elastic objects.