고체역학 (Beer) — Introduction—Concept of Stress: Problem 1.62

1.62 Two brass rods $AB$ and $BC$, each of uniform diameter, will be brazed together at $B$ to form a nonuniform rod of total length $100\text{ m}$ that will be suspended from a support at $A$ as shown. Knowing that the density of brass is $8470\text{ kg/m}^3$, determine (a) the length of rod $AB$ for which the maximum normal stress in $ABC$ is minimum, (b) the corresponding value of the maximum normal stress.