Elasticity (physics)

In physics, elasticity (or stretchiness) is the inherit property of a body which tries to regain its original shape after removal of any deforming force acting on it. Example:- An eraser coming back to its normal shape after being pressed.

Some important definitions

1) Deforming force- A force that changes or tends to change the physical dimensions of a body. 2) Restoring force- It is an internal force which tries to regain its original dimentions after removal of any deforming force. 3) Elastic body - A body that has property of elasticity. 4) Inelasticity(Plasticity)- An inherit property of a body which doesn't regain it's original shape after removal of any deforming force

Transitions to inelasticity

Above a certain stress known as the elastic limit or the yield strength of an elastic material, the relationship between stress and strain becomes nonlinear. Beyond this limit, the solid may deform irreversibly, exhibiting plasticity. A stress-strain curve is one tool for visualizing this transition.

Furthermore, not only solids exhibit elasticity. Some non-Newtonian fluids, such as viscoelastic fluids, will also exhibit elasticity in certain conditions. In response to a small, rapidly applied and removed strain, these fluids may deform and then return to their original shape. Under larger strains, or strains applied for longer periods of time, these fluids may start to flow like a liquid, with some viscosity.

Hooke's law for a spring

In contemporary language, we'd say this as something like extension is directly proportional to force only we'd replace the words "extension" with the symbol (Δx), "force" with the symbol (F), and "is directly proportional to" with an equals sign (=) and a constant of proportionality (k). To show that the springy object was trying to return to its original state, we'd also tack a negative sign (−) in front. In other words, we'd write the equation.

F = − k Δx

Stress

It is force acting per unit area on a body.

Stress=F/A

Strain

It is the ratio of the elongation of the material due to the deforming force(Δl) to the original length of the substance(l)

Strain=Δl/l

Bulk Strain

The ratio of change in volume in the material due to the deforming force to the original volume.

Bulk strain = Δv/v₀

Shear strain

the ratio of relative displacement between the layers to the perpendicular distance from the reference point to the point of application of force.

Young's Modulus

The ratio of longitudinal strain to longitudinal stress.

stress/strain= constant(Y)

hence- Y=Fl/AΔl

Elastic fatigue

Due to repeated application of force, if a body looses the property then it is called to suffer from elastic fatigue.'

Elastic limit

The maximum value of stress within the body regain its original shape is called elastic limit.

See also

• Stiffness
• Elastic modulus
• Linear elasticity
• Pseudoelasticity
• Viscoelasticity
• Resilience
• Plasticity
• Ductility