Collision, impact, and internal over pressure are common causes of which type of stress?

• A. Thermal
• B. Electrical
• C. Chemical
• D. Mechanical

Answer: (D)

Collision, impact, and internal over pressure involve forces that push or squeeze materials, creating strains through the material. When a object collides or strikes, it delivers a loading that the material resists, generating internal stresses. Internal over pressure from a contained substance also acts as a load on the container walls, producing stress distributed through the material. These are classic examples of mechanical stress, which arises from external or internal forces causing deformation. Thermal stress would come from temperature changes causing expansion or contraction, electrical stress from electrical forces, and chemical stress from chemical reactions or interactions—not from direct physical loads like collisions or pressure.