PROBLEM $2$

The beam shown is constructed from four $25-$mm thick boards.

$($a$)$ Determine the maximum value of P that it can support if the allowable shear stress for the wood is $1\mathrm{.}2$ MPa $.($Ignore the nalls$).$

$($b$)$Ignore your answer to part a$)$ and assume that $P=10kN.$ What is the maximum allowable spacing $s$ of the nalls if each nall can resist a shear force of $700$ N $?$