A steel wire of length 4.7m and cross section area 3×10−6m2 stretches by the same amount as a copper wire of length 3.5 m and cross-section area 4×10−6m2 under a given load. The ratio of Young's modulus of steel to that of copper is
1.8
Since the load and extension are the same, ⇒ the ratio YAl sould remain constant.
Therefore,
YsYc=Ac lsAs lc
=4×10−6×4.73×10−6×3.5
=1.8