.3 Forces and elasticity

• The extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
• force = 


  force = spring constant × extension
• F  = k e 

  force, F, in newtons, N

  spring constant, k, in newtons per metre, N/m

  extension, e, in metres, m
• This relationship also applies to the compression of an elastic object, where ‘e’ would be the compression of the object
• A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal