Final answer:
The concept in question is dynamic elongation, which describes the amount a material will stretch when a force is applied, and relates to the elastic properties and tensile stiffness of materials in the field of physics.
Step-by-step explanation:
When a rope-style lifeline stretches due to the force applied to it, this behavior is explained by its elastic properties. The specific term that defines the percentage a material will stretch under tension before returning to its original length is called dynamic elongation. Referring to the question, the correct answer is C) Dynamic elongation. This is a property described by elasticity theory in physics where Young's modulus or elastic modulus (Y) is a factor that indicates how much a material will stretch or compress under a given force. Materials with a higher Young's modulus tend to have higher tensile stiffness, which means they deform less when a force is applied.
Additionally, when we consider materials such as nylon or steel used in ropes or guitar strings, the rope or string's resistance to stretching—referred to as the tensile strength—can be measured. This is a reflection of how a material can resist breaking under tension and is influenced by the proportionality constant k and other characteristics of the material. The behavior of materials under deformation, particularly when it is minimal (less than 0.1% or 1 part in 10³), explains how they will stretch and return to their original shape once the force is removed.