Moment is defined as what?

• A. A force developed when an external load applied transversely to a bridge member causes it to bend.
• B. The amount of energy absorbed before fracture.
• C. The ratio of stress to strain in a material.
• D. The vertical reaction at a support.

Answer: (A)

Moment describes the bending effect a transverse load has on a bridge member. When a load acts across a member, it creates a turning tendency about a point, causing the member to bend. That bending effect is what engineers call the bending moment—a measure of how strongly the load tries to rotate or bend the section, typically calculated as force times its lever arm. In practice, moments are what we map in bending moment diagrams to see where the beam experiences the most bending and where reinforcement is needed. The other concepts refer to different physical quantities: energy absorbed before fracture is a toughness-related idea, the ratio of stress to strain is the modulus of elasticity, and the vertical reaction at a support is simply a reaction force. So the description reflects the bending effect produced by a transverse load, which is the moment.