GCSE Physics 02 — Forces

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Topics include Scalars, Vectors, and Types of Forces, Gravity, Mass, and Weight, Work Done and Power, Energy Stores and Efficiency, Elasticity and Hooke's Law, Elastic Potential Energy, Moments and Equilibrium, and Simple Machines: Levers and Gears.

Physics EN

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Elasticity and Hooke's Law

How forces deform objects, focusing on the linear relationship between force and extension.

Key points

To deform an object (stretch, compress, bend), you need more than one force.
Elastic deformation: Object returns to original shape after force is removed.
Plastic deformation: Object is permanently distorted.
Hooke's Law: Extension is directly proportional to force. $F = k \times e$ ( $k$ is the spring constant in N/m).
Limit of Proportionality: The point beyond which Hooke's Law no longer applies (graph curves).

Worked example

Question

A spring with

k = 40\text{ N/m}

is stretched by

20\text{ cm}

. Calculate the force applied.

Solution

1. Convert units:

20\text{ cm} = 0.2\text{ m}

.
2. Equation:

F = k \times e

.
3. Substitute:

F = 40 \times 0.2

.
4. Answer:

F = 8\text{ N}

Common pitfalls

Forgetting to convert extension from cm to m.
Confusing the length of the spring with the extension (new length - original length).
Assuming Hooke's law applies forever (ignoring the limit of proportionality).

Prerequisites

forces.vectors_scalars_contact
Using SI units

Further resources

BBC Bitesize GCSE Physics: Elasticity and Hooke's Law
Clear GCSE-level explanations and practice questions.

BBC Bitesize · article