AQA GCSE Hooke's Law
Hooke’s Law
Hooke’s Law states:
The extension of an elastic object, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
Examples of elastic objects: Metal springs, elastic bands (when stretched by a small amount), foam mattresses.
Lets break down the definition into parts:
Extension, this is the increase in length.
The original length of the spring is 50mm.
After the 1st weight is added to the spring, the length increases to 72mm.
Extension (after 1st weight added) = 72mm-50mm = 22mm
After the 2nd weight is added, the length increases to 94mm.
Extension (after 2nd weight added) = 94mm-50mm = 44mm
Extension = New length – Original length
Directly proportional
As the force applied increases, so does the extension, as shown by the graph above.
Limit of Proportionality
The limit of proportionality is the point up to which the applied force is directly proportional to extension so Hooke’s law applies.
So, after the limit of proportionality, the force and extension are not directly proportional and the graph line will become curved as shown below.
Practice Questions
1.Define Hooke’s law
2.Does Hooke’s law apply to both compression and stretching for an elastic material?
3. State what is meant by the term limit of proportionality
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