tension

Tension is the pulling force transmitted along the length of a flexible connector, such as a rope, string, or cable, when it is stretched taut. It acts along the member and toward its ends, keeping the component in a state of extension. The concept is used across physics, engineering, and everyday life.

In mechanics, tension is an axial load that produces tensile stress in the material. If a rope of cross-sectional area A carries a force F, the tensile stress is sigma = F/A, and the corresponding axial strain is epsilon = delta L / L. For many materials in the elastic range, sigma ≈ E * epsilon, where E is Young's modulus. In a rope passing over pulleys or subjected to acceleration, tension can vary along its length or between segments; in an ideal massless rope with a single direction, tension is uniform.

Applications include structural cables in bridges and towers, flight lines in cranes, elevator ropes, and tuning of musical strings. Design engineers use safety factors and material limits to ensure that tension under expected loads remains well within allowable stress. Tension is often measured with load cells or sensor networks and can be influenced by dynamic effects such as wind, vibration, or impact loads.

In everyday use, tension appears in clothing, sports equipment, and musical instruments, where it determines stiffness, tone, and playability. In psychology and storytelling, tension refers to a psychological or narrative state of anticipation or suspense arising from potential outcomes, conflicting goals, or time pressure.

A related concept is surface tension, a property of liquids arising from cohesive forces at a liquid’s surface, distinct from the tensile stresses in solids.