a) b) m2 lo lo d+ Ad

Consider a square-faced beam supporting a section of a building.

a)  Before installation, the length of the beam is found to be l₀ = 15.02 m (figure a). After installation and construction, the length is remeasured and found to be l = 14.98 m (figure b). Determine Young's Modulus Y in N/m² for the beam if it supports a mass m = 35000 kg and has a side length d = 1.9 m. 

b) Suppose that after the beam is installed it needs to be repaired. The weight it supports is removed and replaced with a new mass m₂ (figure c). After the new mass is supported, the side length is remeasured and found to be larger with a difference of Δd. Assuming that this side length deformation is uniform and small, write an expression for determining Poisson's ratio v for this beam if its Young's modulus Y is known.