A wire fixed at the upper end stretches by length l by applying a force F. The work done in stretching is

A wire fixed at the upper & stretches by length l by applying a force F. What is the work done by stretching the wire ?

A wire is stretched by one mm by a force of 1 kN. The work done is stretching the wire is

An elastic string of unstretched length L and force constant k is stretched by a small length x. It is further stretched by another small length y. The work done in second stretching is

Two wire of same material and same diameter have lengths in the ratio 2 : 5. They are stretched by same force. The ratio of work done in stretching them is