Elasticity - Hooke's Law
Science: KS3, topic 3.2.24
Hooke's Law
When an object is stretched, its extension is directly proportional to the force applied. We say the object follows Hooke's Law.
Hooke's Law
- When we pull on a spring, it will extend.
- Hooke's Law says the extension will be directly proportional to the force applied.
- So if we double the force, the extension also doubles.
Proportional graph
- If we draw a graph, it shows a directly proportional relationship.
- The graph is a straight line through the origin.
Limit of proportionality
- You can keep increasing the force.
- Eventually, the spring will not return to its original shape.
- We then say the spring has reached its limit of proportionality.
Investigating Hooke's law
- You can investigate Hooke's Law by attaching a spring to a clamp.
- Then, you hang slotted masses on the spring.
- You can then measure the extension of the spring.
Converting to Newtons
- Remember, if the masses are in grams, you will need to convert to Newtons.
- Newtons = mass (kg) x gravitational field strength (m/s2).
Test yourself on Elasticity - Hooke's Law
What does Hooke's Law say?
What is meant by the 'limit of proportionality'?
A spring's extension is directly proportional to the force applied, until the spring passes its limit of proportionality. What happens to a graph of extension against force after this point?
A student hangs masses on a spring. Force (N): 2, 4, 6. Extension (cm): 3, 6, 9. Does this spring obey Hooke's Law?