A carpenter glues a pair of cylindrical wooden logs by bonding their end faces at an angle of $\theta = 30^{\circ}$ as shown in the figure.
The glue used at the interface fails is
Criterion 1: the maximum normal stress exceeds $2.5$ MPa
Criterion 2: the maximum shear stress exceeds $1.5$ MPa
Assume that the interface fails before the logs fail. When a uniform tensile stress of $4$ MPa is applied, the interface
- fails only because of criterion $1$
- fails only because of criterion $2$
- fails because of both criterion $1$ and $2$
- does not fail