IGCSE Physics Revision Guide: Forces, Energy, and Waves

IGCSE Physics is the most mathematical of the three sciences, and that puts some students off. But the maths is actually an advantage — once you understand a formula and how to apply it, you can answer any question that uses it. There’s less ambiguity than in biology or chemistry, and the mark schemes reward clear, logical working.

Here’s a topic-by-topic guide to the key content.

Paper Structure

Cambridge IGCSE (0625)

Core: Paper 1 (multiple choice, 45 min) + Paper 3 (structured, 1 hr 15 min)
Extended: Paper 2 (multiple choice, 45 min) + Paper 4 (structured, 1 hr 15 min)
Practical: Paper 5 or Paper 6

Edexcel International GCSE (4PH1)

Paper 1: 2 hours, two-thirds of the specification
Paper 2: 1 hour 15 minutes, remaining content plus synoptic questions

Forces and Motion

Speed, Velocity, and Acceleration

Know the difference between speed (scalar) and velocity (vector). Be able to calculate:

Speed = distance / time
Acceleration = change in velocity / time
Use of the equation v² = u² + 2as

Distance-time graphs: Gradient = speed. A straight line means constant speed. A curve means changing speed.

Velocity-time graphs: Gradient = acceleration. Area under the graph = distance travelled. These graphs appear on almost every paper — practise interpreting them until it’s second nature.

Forces

Newton’s three laws are the backbone of mechanics at IGCSE:

An object remains at rest or in uniform motion unless acted upon by a resultant force
F = ma (force = mass × acceleration)
Every action has an equal and opposite reaction

Application: Questions often present a scenario (a car braking, an object falling, a rocket launching) and ask you to calculate forces, acceleration, or identify which forces are acting. Draw a force diagram before calculating — it prevents mistakes.

Falling and Terminal Velocity

Objects in free fall accelerate at roughly 10 m/s² (or 9.8 m/s² if the question specifies). When air resistance equals weight, the object reaches terminal velocity and stops accelerating. Be able to describe and sketch the velocity-time graph for a falling object reaching terminal velocity.

Momentum

Momentum = mass × velocity. Conservation of momentum in collisions is a key principle. Practise both elastic and inelastic collision calculations.

Extended content: Impulse (force × time = change in momentum) connects force, time, and momentum. This explains why airbags work — they increase the time over which momentum changes, reducing the force on the body.

Energy

Types of Energy and Energy Transfers

Know the main types: kinetic, gravitational potential, elastic potential, thermal, chemical, nuclear, electrical, and sound. Be able to describe energy transfers in specific scenarios using these terms.

Conservation of Energy

Energy cannot be created or destroyed, only transferred. In calculations, this means:

KE gained = GPE lost (for falling objects, neglecting air resistance)
½mv² = mgh

Efficiency

Efficiency = useful energy output / total energy input (× 100 for percentage). Many exam questions involve calculating efficiency from energy diagrams or data tables.

Power

Power = energy transferred / time = work done / time. Units: watts (W). A common calculation involves linking power, force, and speed: P = Fv.

Waves

General Wave Properties

Know these definitions precisely:

Wavelength (λ): Distance between two consecutive identical points on a wave
Frequency (f): Number of complete waves passing a point per second (Hz)
Amplitude: Maximum displacement from the rest position
Period (T): Time for one complete wave (T = 1/f)

The wave equation: v = fλ. You’ll use this constantly.

Transverse and Longitudinal Waves

Transverse: Oscillation is perpendicular to the direction of travel (e.g., light, water waves)
Longitudinal: Oscillation is parallel to the direction of travel (e.g., sound)

Be able to identify which type a wave is from a description or diagram.

Sound

Sound is a longitudinal wave that requires a medium to travel. Know:

Speed of sound in air ≈ 340 m/s
How to calculate distance using echoes (remember the sound travels there AND back)
The relationship between frequency and pitch, amplitude and loudness

Light

Reflection: angle of incidence = angle of reflection
Refraction: light changes speed and direction when moving between media
Total internal reflection and critical angle (extended)
Converging lenses: ray diagrams, real and virtual images (extended)

Exam focus: Ray diagrams must be drawn accurately with a ruler. Label all angles and use correct conventions (normal line, direction arrows).

The Electromagnetic Spectrum

Know the order: radio, microwave, infrared, visible light, ultraviolet, X-rays, gamma rays. For each, know at least one use and one hazard. All electromagnetic waves travel at 3 × 10⁸ m/s in a vacuum.

Electricity

Circuit symbols and diagram drawing
Current, voltage, and resistance (V = IR)
Series and parallel circuits: how current and voltage distribute
Power: P = IV = I²R = V²/R
Electrical energy: E = Pt = IVt

Practical tip: When solving circuit problems, write down everything you know, identify what you need to find, and choose the appropriate formula. Being systematic prevents confusion in multi-step problems.

Exam Technique

Show Your Working

Physics is mathematical. Method marks are awarded for correct working, even if the final answer is wrong. Write the formula, substitute the values, calculate the result, and include units.

Units

Always convert to SI units before calculating. Kilometres to metres, minutes to seconds, kilowatts to watts. The most common way to lose marks in physics is a unit conversion error.

Graphs

When drawing graphs: use a sharp pencil, plot points accurately, draw a smooth best-fit line (not dot-to-dot), label axes with quantity and unit, and choose a sensible scale.

When reading graphs: identify the gradient, the y-intercept, or the area under the curve, depending on what the question asks. State what these represent physically.

Past Paper Practice

Physics past papers are repetitive in the best possible way. The same types of calculation appear regularly, and familiarity with the format builds both speed and confidence.

UpGrades provides IGCSE Physics practice aligned to Cambridge and Edexcel specifications, focusing on the calculation-heavy topics that carry the most marks.

Master the formulae, practise the calculations, and develop a systematic approach to problems. Physics rewards precision and method — give the examiner a clear trail to follow, and the marks look after themselves.