Hooke's Law (AQA GCSE Combined Science: Trilogy: Physics): Revision Note

Hooke's Law

What is Hookes' Law?

• The relationship between the extension of an elastic object and the applied force is defined by Hooke's Law

• Hooke's Law states that:

  The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality

• Directly proportional means that as the force is increased, the extension increases 

  • If the force is doubled, then the extension will double

  • If the force is halved, then the extension will also halve

• The limit of proportionality is the point beyond which the relationship between force and extension is no longer directly proportional 

  • This limit varies according to the material

Hooke's Law states that a force applied to a spring will cause it to extend by an amount proportional to the force, this can be tested by this Hooke's Law experiment

Using Hooke's Law

Hooke's Law Equation

• Hooke's Law is defined by the equation:

F = k × e

• Where:

  • F = force in newtons (N)

  • k = spring constant in newtons per metres (N/m)

  • e = extension in metres (m)

• The symbol e can represent either the extension or compression of an elastic object

• The spring constant represents how stiff a spring is

  • The higher the spring constant, the higher the stiffness

• The extension of an object can be calculated by:

final length – original length

• The extension of the spring can be measured by marking the position of bottom of the unstretched spring

• When the spring is stretched the final length must be measured from the bottom of the spring

Force, extension and spring constant are used to define Hooke's Law

• The Hooke's Law equation can be rearranged with the help of the following equation triangle: