Hooke's Law (CIE IGCSE Physics)

EXTENDED

• Hooke’s law states that:
  • The extension of a spring is proportional to the applied force

• Where:
  • F is the force applied
  • k is the spring constant
  • x is the extension of the spring

• The spring constant is the force per unit extension
  • The units are N/m
  • The spring constant is a measure of how stiff the spring is

• Many other materials (such as metal wires) also obey Hooke’s law
• Hooke’s law is associated with the initial linear (straight) part of a force-extension graph
• Objects that obey Hooke’s law will return to their original length after being stretched
• If an object continues to be stretched it can be taken past the limit of proportionality (sometimes called the elastic limit). At this point the object will no longer obey Hooke’s law and will not return to its original length

The spring on the right has been stretched beyond the limit of proportionality