👉 Stiffness or rigidity is a property in which an object remains rigid and does not deform when subjected to forces. In physics, it refers to the resistance of an object to change its shape under a given force. Stiffness can be caused by many factors such as material properties, strain, temperature, and external forces. For example, a spring is a common example of stiffness because it has a constant spring constant (a measure of how much the spring stretches or contracts) that remains constant