Concept:
The maximum elongation happens when the stress acting on the body is maximum.
\(\displaystyle \Delta l=\frac{Pl}{AE}=\frac{σ_{max} l}{E}\)
σmax = maximum tensile stress, l = length, and E = Young Modulus of Elasticity.
Calculation:
Given:
l = 300 mm, σmax = 270 MPa, E = 100 GPa = 100 × 103 MPa
\(\displaystyle \Delta l=\frac{σ_{max} l}{E}\)
\(\displaystyle \Delta l=\frac{270 \times 300}{100\times10^3}=0.81\;mm\)