• The relationship between the extension of an elastic object and the applied force is defined by?Hooke's Law
• Hooke's Law states that:

The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality

• Directly proportional means that as more force is applied, the greater the extension (and vice versa)
• The?limit of proportionality?is where if more force is added, the object may extend but will?not?return to its original shape when the force is removed (it will be?inelastically?deformed)
  • This limit varies according to the material

   

Hooke's Law states that a force applied to a spring will cause it to extend by an amount proportional to the force

The Force-Extension Graph

• Hooke’s law is the?linear?relationship between force and extension
  • This is represented by a?straight line?on a force-extension graph

   

• Any material beyond its?limit of proportionality?will have a non-linear relationship between force and extension

Hooke's Law is associated with the linear region of a force-extension graph

• When some objects, such as springs or rubber bands, are stretched they will return to their original shape and length once the forces are removed
  • Other materials, such as plastic, remain permanently deformed (stretched)

   

• A change of shape is called a?deformation?and can either be:
  • Elastic
  • Inelastic

   

Elastic Deformation

• Elastic deformation occurs:

When objects return to their original shape when the stretching force is removed

• Examples of materials that undergo elastic deformation are:
  • Rubber bands
  • Fabrics
  • Steel springs

   

Inelastic Deformation

• Inelastic deformation occurs:

When objects remain stretched and do not return completely to their original shape even when the stretching force is removed

• Examples of materials that undergo inelastic deformation are:
  • Plastic
  • Clay
  • Glass

轉載自savemyexams