Hooke’s Law states that the strain of the material is proportional to the applied stress within the elastic limit of that material. 

When the elastic materials are stretched, the atoms and molecules deform until stress is been applied and when the stress is removed they return to their initial state.

When force is applied to a material, we know that it either stretches or compresses in response to the applied force. In mechanics, the force applied per unit area is known as stress and is denoted by the symbol σ. The extent to which the material compresses or stretches is known as strain. Different materials respond differently to applied stress.  This information is necessary for engineers while selecting materials for their structures.

Mathematically, Hooke’s law is commonly expressed as:

Where,

• F is the force
• x is the extension length
• k is the constant of proportionality known as spring constant in N/m