Hooke's Law

Overview

This lesson turns the spring investigation into a scientific relationship. You are looking for the pattern between force and extension, showing it on a graph, and then using that pattern to explain Hooke’s law.

What You Need to Know

• Hooke’s law states that the extension of a spring is directly proportional to the force applied, as long as the limit of proportionality is not exceeded.
• On a graph of force against extension, direct proportionality appears as a straight line through the origin.
• The gradient of the graph is linked to the spring constant.
• A larger spring constant means a stiffer spring.
• Graphs, equations, and practical results should all tell the same story if the data is good.

How to Work Through It

1. Start by reviewing the results from the springs investigation.
2. Plot or interpret a force-extension graph and look for the overall pattern.
3. Link the straight-line pattern to Hooke’s law.
4. Use the graph or equation to calculate a spring constant and explain what it means.

Check Your Understanding

• What does directly proportional mean in this context?
• How would the graph show that Hooke’s law is being followed?
• What does the spring constant tell you about the spring?
• When would Hooke’s law stop being a good model for the spring?

Common Mistakes

• Mixing up length and extension.
• Saying any straight line shows direct proportion. It must also pass through the origin.
• Treating the spring constant as just a number without linking it to stiffness.
• Ignoring the idea that the relationship only works up to the limit of proportionality.

Next Steps

• Use the worksheet questions to practise moving between the graph, words, and equation.
• Keep the idea of spring constant secure because the next lesson focuses on calculations.