- For a material which obeys Hooke's law, the elastic strain energy, Eel can be determined by finding the area under the force-extension graph
- Since this area will be a triangle with sides F (force) and x (extension) the equation is:
- Eel = elastic strain energy (or work done) (J)
- F = average force (N)
- Δx = extension (m)
- Since Hooke's Law states that F = kΔx, the elastic strain energy can also be written as:
- k = spring constant (N m–1)
The graph shows the behaviour of a sample of a metal when it is stretched until it starts to undergo plastic deformation.What is the total work done in stretching the sample from zero to 13.5 mm extension?
Simplify the calculation by treating the curve XY as a straight line.
Make sure that you are familiar with the area of common 2D shapes such as a square, rectangle, right-angled triangle and trapezium. Don't forgot to split the area of the graph up into these easier shapes and add up the area of each section for more complicated graphs! Always look at the units of the extension and the force, and check any unit conversions before giving your final answer.