Question $2$: The beam is constructed from two boards fastened together with three rows of nails spaced $s=50mm$ apart. If each nail can support a $2\mathrm{.}25kN$ shear force, determine the maximum shear force that can be applied to the beam. The allowable shear stress for the wood is ${}_{\text{a}\text{l}\text{l}\text{o}\text{w}}=2\mathrm{.}1$MPa.