Given:
Steel cable’s length, I = 9.1 m
Radius, r = 5mm = 5 × 10-3 m.
Tension in cable, F = 800 N
Young’s modulus = 2 × 1011 N/m2
Young’s modulus,
Y = \(\frac{F}{A}\) × \(\frac{l}{∆l}\)
Or ∆l = \(\frac{F}{πr^2}\) × \(\frac{l}{Y}\)
= \(\frac{800×9.1}{3.14×(5×10^{−3})^2×2×10^{11}}\)
= 4.64 × 10-4 m