Bending Stress MCQ with answer and solution

Concept

Curvature at section of zero bending moment

Formula

κ = 1 / R = M / (EI)

Step-by-step solution

1. The flexure formula relates bending moment to curvature as M / I = E / R. 2. Rearranging gives curvature κ = 1 / R = M / (EI). 3. When bending moment M = 0 at a section, κ = 0 / (EI) = 0. 4. Thus, the curvature at that cross section is zero. Answer: B

Explanation

Curvature of a bent beam is defined as κ = 1/R = M/(EI). At any cross section where the bending moment M equals zero, the curvature κ is identically zero.

Why the other options are wrong

A) Infinity is the radius of curvature R, whereas curvature 1/R is zero. C) Curvature varies with moment and is not constant across differing moment sections. D) For zero moment, curvature is unconditionally zero regardless of load pattern.

Shortcut

Curvature κ is zero where M = 0; radius of curvature R is infinity.

Common mistake

Confusing curvature κ (which is zero) with the radius of curvature R (which tends to infinity).