a) Elastic potential energy

a) force–extension (or compression) graph; work done is area under graph

b) elastic potential energy; E = ½Fx; E = ½kx²

the area under a force extension graph = work done/elastic potential energy

E = ½Fx

• elastic potential energy of the spring (J) = ½ × force applied to the spring (N) × extension/compression of the spring (m)

E = ½kx²

• elastic potential energy of the spring (J) = ½ × force constant of the spring (Nm^-1) × extension/compression of the spring² (m²)