Identify the stress–strain pair: equal and opposite tangential forces across a resisting section cause the body to tend to slide (shear) on that section. What stress and strain arise?

Introduction / Context:
Different external loadings generate distinct internal stress and associated strain responses. Recognizing shear scenarios is crucial in connections, rivets, welds, and beam webs where sliding along a plane is critical.

Given Data / Assumptions:

• Two equal and opposite tangential forces acting across a section.
• Forces act parallel to the area, not normal to it.
• Small deformations; linear elasticity.

Concept / Approach:
When loads act tangentially to a surface, the internal response is shear. The related strain measure is change in angle (distortion) between originally orthogonal lines—this is shear strain, usually denoted gamma.

Step-by-Step Solution:

Verification / Alternative check:
Mohr’s circle for stress shows pure shear produces equal magnitude principal stresses of opposite signs; strain counterpart displays angular change, not axial extension alone.

Why Other Options Are Wrong:
Tensile/compressive pairs result from normal forces; shear stress with tensile strain is mismatched.

Common Pitfalls:
Confusing axial and tangential loadings; assuming all deformations are axial elongations instead of angular distortions under shear.

Final Answer:

shear stress, shear strain