Hooke's Law
- A material obeys Hooke’s Law if its extension is directly proportional to the applied force (load)
- The Force v Extension graph is a straight line through the origin (see “Extension and Compression”)
- This linear relationship is represented by the Hooke’s law equation
Hooke’s Law
- The constant of proportionality is known as the spring constant k
Worked example
A spring was stretched with increasing load.
The graph of the results is shown below.
What is the spring constant?
Examiner Tip
Double check the axes before finding the spring constant as the gradient of a force-extension graph. Exam questions often swap the load onto the x-axis and length on the y-axis. In this case, the gradient is not the spring constant but 1 ÷ gradient is.