A wire has a cross sectional area ‘A’, length ‘L’ and young’s modulus ‘Y’. It is pulled by a force ‘F’ which causes a total extension of length ‘l’. The force F is so adjusted that the wire is only slowly stretched. Find the work done by the force in pulling the string by a length ‘dx’ when extension is x (0 > x > l).

Elastic modulus measures the resistance of the material to elastic—or “springy”—deformation.

Low modulus materials are floppy and stretch a lot when they are pulled (squash down a lot when pushed). High modulus materials are opposite—they stretch very little when pulled (squash down very little when pushed).