P$\mathrm{.}18\mathrm{.}13$ Determine the maximum shear stress in the beam section shown in Fig. P$\mathrm{.}18\mathrm{.}13,$ stating clearly the point at which it occurs. Determine also the rate of twist of the beam section if the shear modulus $G$ is $25,000\frac{N}{m}{m}^2.$

Answer: $,70\mathrm{.}2\frac{N}{m}{m}^2$ on the underside of $24$ at $2$ or on the upper surface of $32at2\mathrm{.}9\mathrm{.}0{10}^{-4}$rad$/$mm

FIGURE P$.18\mathrm{.}13$