What is the standard formula for stress in a material under load?

• A. F / A
• B. A / F
• C. sigma = F / A
• D. F * A

Answer: (C)

Stress is the internal resisting force per unit area that a material develops when loaded. The standard way to express this is sigma = F / A, where F is the applied force and A is the cross-sectional area. This shows clearly how the same force becomes more stressful on a smaller area and less stressful on a larger area. Using the sigma symbol emphasizes that we’re talking about stress, not just any ratio of force to area. Writing it exactly as sigma = F / A matches the established notation used in engineering and materials science, which is why it’s the best choice. The other forms misrepresent the concept: A / F would invert the relationship and do not describe stress, and F multiplied by A yields a quantity with different units and meaning. When F is in newtons and A in square meters, the stress is measured in pascals (N/m^2).