Within the limits of elasticity, the ratio of the linear stress
to the linear strain is termed the modulus of elasticity or
Young's Modulus and may be written Young's Modulus, or
E =(Stress/Strain) It is this property that determines how
much a bar will sag under its own weight or under a
loading when used as a beam within its limit of
proportionality. For steel, Young's Modulus is of the order
of 205000 N/mm2.