Problem $01\mathrm{.}016-$ Shear in a dry mortise joint

Two wooden planks, each $\frac{1}{2}$ in$.$ thick and $9$ in $.$ wide, are joined by the dry mortise joint shown. Knowing that the wood used shears off

along its grain when the average shearing stress reaches $1\mathrm{.}8$ ksi $,$ determine the magnitude $P$ of the axial load that will cause the joint to

fail.

The magnitude $P$ of the axial load that will cause the joint to fail is

kips.