Elastic Potential Energy and Springs

This lesson covers elastic potential energy and Hooke's law as required by the Edexcel GCSE Physics specification (1PH0), Topic 3: Conservation of Energy. You need to understand how energy is stored in stretched or compressed springs, use the relevant equations, and know the core practical for investigating Hooke's law.

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Hooke's Law

When a spring is stretched or compressed by a force, it extends (or compresses) proportionally — as long as the limit of proportionality is not exceeded.

The Equation

$F = k x$F=kx

Where:

• F = force applied (newtons, N)
• k = spring constant (newtons per metre, N/m)
• x = extension (metres, m)

What Is the Spring Constant?

The spring constant (k) tells you how stiff a spring is:

• A large spring constant means the spring is stiff — it needs a large force to produce a small extension.
• A small spring constant means the spring is soft — a small force produces a large extension.
• The units of the spring constant are N/m (newtons per metre).