Applications of elasticity

The elastic behaviour of materials, and specifically how much a beam bends under a given load, is a major structural-engineering concern for the stability of buildings and bridges. A bridge must be designed to carry the load of flowing traffic, the force of wind, and its own weight, all without excessive bending, and 'the amount of stress the design can withstand' is a primary safety factor engineers must calculate. To reduce the bending of a beam for a given load, the design should use a material with a HIGHER Young's modulus -- Table 7.1 shows steel's Young's modulus (20.0 x 10^10 N/m^2) is greater than that of aluminium, copper, or glass, with iron (19.0 x 10^10 N/m^2) coming in close behind steel; this is exactly why steel is the material of choice for the design of heavy-duty machines, and iron rods are the material of choice for reinforcing the concrete of buildings. A related everyday question -- which is more elastic, rubber or steel -- is answered directly from the definition of Young's modulus: for the SAME applied stress, steel produces much LESS strain than rubber does, meaning steel's Young's modulus is far higher than rubber's. Since the object with the higher Young's modulus is, by the physics definition, the MORE e …