고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.81

2.81 Two blocks of rubber, each of width \(w = 60 \text{ mm}\), are bonded to rigid supports and to the movable plate \(AB\). Knowing that a force of magnitude \(P = 19 \text{ kN}\) causes a deflection \(\delta = 3 \text{ mm}\) of plate \(AB\), determine the modulus of rigidity of the rubber used.