When a bending moment acts on a beam section, internal stresses develop to resist it. What is the name of this internal resistance to bending?

Introduction / Context:
Beams under transverse loads experience internal stress distributions. Distinguishing bending stress from shear stress is essential for sizing members and checking combined stress states.

Given Data / Assumptions:

• A prismatic beam resists an external bending moment M.
• Linear elastic material; plane sections remain plane.
• Neutral axis passes through the centroid of the section for homogeneous members.

Concept / Approach:
Bending stress is the normal stress that varies linearly with distance from the neutral axis due to bending moment. The classic relationship is sigma = M * y / I, where y is the distance from the neutral axis and I is the second moment of area.

Step-by-Step Solution:

Verification / Alternative check:
Integrate sigma(y) over the cross-section to recover the internal moment: ∫ sigma * y dA = M, confirming that bending stress is the resisting mechanism.

Why Other Options Are Wrong:
Compressive or shear stress alone are incomplete descriptions; bending generates both tension and compression varying with y, not purely shear. Elastic modulus is a material property, not a stress.

Common Pitfalls:
Confusing shear stress (from transverse shear force) with bending stress (from moment); assuming uniform stress rather than linear distribution.

Final Answer:

bending stress