# Elastic Strain Energy

• Up to the elastic limit of a sample, all the work done in stretching it is stored potential energy, or Elastic Strain Energy. This value can be determined by calculating the area under the the force-extension graph. If the sample obeys Hooke’s Law, and is below the elastic limit, the Elastic Strain Energy can be calculated by the formula:
E = ½Fx
• Or, since F = kx (where k is the stiffness constant of the sample):
E = ½kx2