Unit Overview

Motion, Forces and Energy

CIE IGCSE Physics· 5 min read 📊 15-20% of both MCQ (Papers 1/2) and Theory (Papers 3/4) sections

1. Unit at a glance

The unit follows a logical learning sequence: it opens with foundational measurement skills, moves to descriptions of linear motion, explores the forces that change motion, then covers energy transfer, energy resources, and pressure in solids and fluids. Extended-only content is clearly marked for students taking the higher-tier syllabus.

Concepts build incrementally, so work through subtopics in the listed order to avoid gaps in understanding, and reference the unit cheatsheet for quick cross-subtopic formula reminders.

Work through the following subtopics in order to build your knowledge step-by-step:

Physical Quantities and Measurement Techniques

Learn SI units, prefixes, and practical measurement methods for length, time, volume and mass.

★★⏱ 8 min

Speed, Velocity and Motion Graphs

Calculate speed, velocity and acceleration, and interpret distance-time and velocity-time graphs for linear motion.

★★★⏱ 10 min

Mass, Weight and Density

Distinguish between mass and weight, and calculate density of regular, irregular and fluid substances.

★★⏱ 7 min

Forces, Elasticity and Newton's Laws

Identify types of forces, explore elastic deformation, and apply Newton's three laws of motion to solve problems.

★★★⏱ 12 min

Moments and Centre of Gravity

Calculate turning moments of forces, analyse equilibrium systems, and locate centre of gravity for regular objects.

★★★⏱ 9 min

Momentum and Impulse (Extended Only)

Calculate linear momentum and impulse, and apply the principle of conservation of momentum to collisions.

★★★★⏱ 10 min

Energy, Work and Power

Identify forms of energy, calculate work done, power output, and energy transfers between systems.

★★★⏱ 10 min

Energy Resources and Efficiency

Evaluate renewable and non-renewable energy resources, and calculate energy efficiency of systems.

★★⏱ 7 min

Pressure

Calculate pressure in solids, liquids and gases, and apply the hydraulic pressure principle to real systems.

★★★⏱ 9 min

2. Common Pitfalls

Wrong move:

Confusing mass and weight in force calculations

Why:

Mass is a scalar measure of matter in kg, while weight is a gravitational force measured in Newtons

Correct move:

Always convert mass to weight using $W = m g$ when calculating forces involving gravity

Wrong move:

Mixing up distance-time and velocity-time graph gradients

Why:

Gradient of a distance-time graph is speed, while gradient of a velocity-time graph is acceleration

Correct move:

Label graph axes first before interpreting gradients or areas under curves

Wrong move:

Using force alone to calculate work done

Why:

Work done requires both force and the distance moved in the direction of the applied force

Correct move:

Use $W = F \times d$ , ensuring $d$ is the distance parallel to the applied force

3. Quick Reference Cheatsheet

Concept/Formula	Relevant Subtopic	Key Note
$v = \frac{Δ d}{Δ t}$	Speed, Velocity and Motion Graphs	Average speed = change in distance / change in time
$W = m \times g$	Mass, Weight and Density	Weight = mass × gravitational field strength ( $g \approx 9.8$ N/kg on Earth)
$ρ = \frac{m}{V}$	Mass, Weight and Density	Density = mass / volume, units kg/m³ or g/cm³
$F = m \times a$	Forces, Elasticity and Newton's Laws	Resultant force = mass × acceleration
$M = F \times d$	Moments and Centre of Gravity	Moment of a force = force × perpendicular distance from pivot
$p = m \times v$	Momentum and Impulse (Extended Only)	Momentum = mass × velocity, conserved in closed systems
$W = F \times d$ , $P = \frac{W}{t}$	Energy, Work and Power	Work done = force × distance; Power = work done / time
$P = \frac{F}{A}$ , $P = ρ g h$	Pressure	Pressure = force / area; Pressure in liquid = density × g × depth

What's Next

Start your study of this unit with the first subtopic on physical quantities and measurement techniques, as these foundational skills are required for all subsequent calculations and practical activities in this unit and later IGCSE Physics content. Once you complete all subtopics in Unit 1, you will move on to Unit 2 covering Thermal Physics, which builds on the energy concepts you will learn here. Test your understanding with end-of-subtopic quizzes before progressing to more advanced content.