One end of a steel wire is fixed to the ceiling of a moving elevator. A load of $20\text{kg}$ hangs from the other end. If the elevator is moving up with an acceleration $1{\text{m/s}}^2$ and Area of cross- section of wire is $2{\text{cm}}^2$ then find the longitudnal strain in the wire.

[Take $g=10{\text{ms}}^{-2},Y=2\times {10}^{11}{\text{Nm}}^{-2}$ ]