Final answer:
The constants for the strain-life curve depend on factors specific to the material. For example, different materials may have different values for the constant depending on their properties. For small deformations, most materials return to their original lengths when the force is removed.
Step-by-step explanation:
The constants for the strain-life curve depend on several factors for the material being studied. For example, the elongation of a guitar string made of nylon is proportional to the force applied, implying a larger constant for thicker nylon strings or ones made of steel. The constants also determine the behavior of materials when the force is removed, with most materials returning to their normal lengths if the deformation is small.