Solution to Problem 515 | Flexure Formula

At section b-b:
$\sin \theta = \dfrac{z}{2} = \dfrac{3}{5}$

$z = 1.2 \, \text{m}$
 

$M = zR_B - 200z\,(z/2)$

$M = 1.2(500) - 200(1.2)(1.2/2)$

$M = 456 \, \text{N}\cdot\text{m}$
 

$f_b = \dfrac{Mc}{I} = \dfrac{456(1000)(50/2)}{\dfrac{50(50^3)}{12}}$

$f_b = 21.888 \, \text{ MPa}$           answer