Stress in physics is a measure of the internal forces within a material that can cause it to deform or change shape. It is typically measured in units of force per unit area, such as pounds per square inch (psi) or Newtons per square meter (N/m^2).
Stress is calculated by dividing the force applied to a material by the cross-sectional area over which the force is applied. This gives a measure of the force per unit area, and is represented by the formula stress = force/area.
Strain in physics is a measure of the deformation or change in shape that occurs in a material when stress is applied to it. It is typically expressed as a percentage, and is calculated by dividing the change in length or shape by the original length or shape of the material.
Stress and strain are directly related to each other, as stress is the cause of strain. The greater the applied stress, the greater the resulting strain in a material. This relationship is often expressed as Hooke's Law, which states that within the elastic limit, stress is directly proportional to strain.
In physics, there are three main types of stress: tensile stress, compressive stress, and shear stress. Similarly, there are three main types of strain: tensile strain, compressive strain, and shear strain. These types of stress and strain describe the different ways in which a material can be deformed when subjected to external forces.