Elasticity exists in metals in three distinct ways:
First, in the form of traction. Hang a weight on a wire and it will stretch a certain amount. When the weight is removed the wire shrinks back to its original length.
Second: If the weight on the wire is rotated, so as to twist it, and the hand is taken from the weight, it will untwist itself, and go back to its original position. This is called torsion.
Third: A piece of metal may be coiled up like a watch spring, or bent like a carriage spring, and it will yield when pressure is applied. This is called flexure.
Certain kinds of steel have these qualities in a high degree.
Title: Practical Mechanics for Boys
Author: J. S. Zerbe