고체역학 (Beer) — Analysis and Design of Beams for Bending: Problem 5.33

5.33 A solid steel bar has a square cross section of side \( b \) and is supported as shown. Knowing that for steel \( \rho = 7860 \text{ kg/m}^3 \), determine the dimension \( b \) for which the maximum normal stress due to bending is (a) \( 10 \text{ MPa} \), (b) \( 50 \text{ MPa} \).