Deformation occurs when solids experience tensile (stretching) or compressive (squeezing) forces in one dimension.
6.1.2 Terms related to deformation:
Load: The force applied to a solid.
Extension: The increase in length of a solid when subjected to a tensile force.
Compression: The decrease in length of a solid when subjected to a compressive force.
Limit of proportionality: The maximum stress at which Hooke's law is valid, beyond which the material exhibits non-linear behavior.
6.1.3 Hooke's law:
Hooke's law states that the extension of a spring or elastic material is directly proportional to the applied force, as long as the elastic limit is not exceeded.
Mathematically, F = kx, where F is the applied force, x is the extension, and k is the spring constant.
6.1.4 Young modulus:
The Young modulus (Y) is a measure of the stiffness of a material and is defined as the ratio of stress to strain.
Young modulus (Y) = stress / strain.
6.1.5 Determining the Young modulus:
An experiment can be conducted to determine the Young modulus of a metal wire. This typically involves measuring the extension of the wire under different loads and calculating the stress and strain values.
6.2 Elastic and plastic behavior:
6.2.1 Elastic deformation:
Elastic deformation occurs when a material returns to its original shape after the applied force is removed.
6.2.2 Plastic deformation:
Plastic deformation occurs when a material undergoes permanent deformation and does not return to its original shape after the applied force is removed.
6.2.3 Force-extension graph and work done:
The area under a force-extension graph represents the work done on the material during deformation.
6.2.4 Elastic potential energy:
For a material deformed within its limit of proportionality, the elastic potential energy (EP) can be calculated using EP = 1/2 Fx = 1/2 kx2, where F is the applied force, x is the extension, and k is the spring constant.