DEFORMATION OF SOLIDS

State Hookes law

The extension of an elastic material is directly proportional to the load applied provided the limit of proportionality is not exceeded

What is the equation for hookes law

F = kx

Define elastic deformation

Temporary deformation of a material which is fully reversed when the load is removed

Define limit of proportionality

The point beyond which hookes law is no longer true when deforming a material

Define elastic limit

The maximum load which can be applied that allows the material to return to its original length when the load is removed

Define plastic limit

The permanent deformation that is not reversed when the load is removed

Define tensile stress

The force applied per unit cross sectional area of the material

What is the equation for tensile stress

Stress = F / A

Define tensile strain

The ration of the change in length of the material to its original length

What is the equation for tensile strain

Strain = x / Lo

Define young modulus

The ratio of the stress to strain

What is the derived equation for the young modulus

E = FLo / Ax

How can the young modulus be determined experimentally

Measure the extension of a wire of known length and cross sectional area for a range of loads

How do you work out the young modulus form a load- extension graph

E = gradient x Lo / A

How do you find the young modulus of a stress- strain graph

Find the gradient

How can you find the potential energy store in a stress-strain graph

Area under the graph

What equations are used to find energy stored in a spring

E = ½ fx or E = ½ kx²