A student can understand a Physics concept and still lose marks when a calculation requires the correct equation, unit conversion or rearrangement. The difference often comes down to knowing how to apply the formula, not simply remembering it.

This Cambridge IGCSE Physics formula sheet brings together the key equations from the 0625 syllabus for examinations in 2026, 2027 and 2028. It covers Motion, Forces and Energy, Thermal Physics, Waves, Electricity and Magnetism, Nuclear Physics and Space Physics.

Each section explains what the equation is used for, defines its symbols and includes worked examples to help students apply them to numerical questions.

Use this guide to revise the equations required for your examination route. Core candidates need the Core content. Extended candidates need both Core and Supplement content.

Cambridge IGCSE Physics 0625: Core and Extended

Before revising the equations, identify which examination route you are following.

Core

Core candidates study the Core syllabus content and take the relevant Core examination papers.

Extended

Extended candidates study both Core and Supplement content. They need to prepare for the additional equations and concepts included in the Supplement syllabus.

Both routes also include a practical assessment through the relevant practical examination component.

The Supplement labels in this guide identify additional content for Extended candidates. Students taking Extended should revise the Core equations as well.

1. Motion and Acceleration Formulas

Motion questions examine how an object moves, how quickly it travels and how its velocity changes over time.

Speed

Formula:

Speed = Distance ÷ Time

Symbols and units:

• Speed (v): metres per second (m/s)
• Distance (s): metres (m)
• Time (t): seconds (s)

Syllabus: Core

Use this equation when a question gives the distance travelled and the time taken.

Average Speed

Formula:

Average speed = Total distance travelled ÷ Total time taken

Syllabus: Core

Use the total journey distance and total journey time, including periods when the object is stationary if they are part of the stated journey.

Acceleration

Formula:

a = Δv ÷ Δt

Where:

• a = acceleration (m/s²)
• Δv = change in velocity (m/s)
• Δt = time taken (s)

Syllabus: Core

Acceleration describes how quickly velocity changes. Deceleration is negative acceleration.

Acceleration from a Speed–Time Graph

Formula:

Acceleration = Gradient of the speed–time graph

A steeper gradient represents a greater acceleration. A negative gradient represents deceleration.

Syllabus: Core

Distance from a Speed–Time Graph

Method:

Distance travelled = Area under the speed–time graph

For a rectangular section:

Area = Base × Height

For a triangular section:

Area = ½ × Base × Height

Syllabus: Core

2. Forces and Hooke's Law Formulas

Forces can change an object's speed, direction or shape. In IGCSE Physics, students need to understand force, mass, acceleration, moments and the behaviour of springs.

Weight and Gravitational Field Strength

Formula:

g = W ÷ m

Rearranged:

W = mg

Where:

• g = gravitational field strength (N/kg)
• W = weight (N)
• m = mass (kg)

Syllabus: Core

Near the Earth's surface, gravitational field strength is approximately 9.8 N/kg.

Hooke's Law and Spring Constant

Formula:

k = F ÷ x

Rearranged:

F = kx

Where:

• k = spring constant (N/m)
• F = applied force (N)
• x = extension (m)

Syllabus: Supplement

The spring constant describes how much force is required to produce a unit of extension. A larger spring constant indicates a stiffer spring.

Limit of Proportionality

The limit of proportionality is the point on a load–extension graph beyond which extension is no longer directly proportional to the applied load.

Students should be able to:

• Plot a load–extension graph.
• Identify the straight-line section.
• Locate the limit of proportionality.
• Interpret the relationship between force and extension.

Syllabus: Supplement

Newton's Second Law

Formula:

F = ma

Where:

• F = resultant force (N)
• m = mass (kg)
• a = acceleration (m/s²)

Syllabus: Supplement

The resultant force and acceleration act in the same direction.

Moment of a Force

Formula:

Moment = Force × Perpendicular distance from pivot

Where:

• Moment = newton metre (N m)
• Force = newton (N)
• Perpendicular distance = metre (m)

Syllabus: Core

Use the perpendicular distance from the pivot, not the length of the object unless that length is perpendicular to the force.

3. Density, Momentum and Pressure Formulas

Density

Formula:

ρ = m ÷ V

Where:

• ρ = density (kg/m³ or g/cm³)
• m = mass (kg or g)
• V = volume (m³ or cm³)

Syllabus: Core

Make sure mass and volume are expressed in compatible units before calculating density.

Momentum

Formula:

p = mv

Where:

• p = momentum (kg m/s)
• m = mass (kg)
• v = velocity (m/s)

Syllabus: Supplement

Impulse

Formula:

Impulse = FΔt = Δ(mv)

Where:

• F = resultant force (N)
• Δt = time interval (s)
• Δ(mv) = change in momentum (kg m/s)

Syllabus: Supplement

Resultant Force and Change in Momentum

Formula:

F = Δp ÷ Δt

Where:

• Δp = change in momentum (kg m/s)
• Δt = time taken (s)

Syllabus: Supplement

Pressure

Formula:

p = F ÷ A

Where:

• p = pressure (Pa)
• F = force (N)
• A = area (m²)

Syllabus: Core

Pressure Beneath a Liquid Surface

Formula:

Δp = ρgΔh

Where:

• Δp = change in pressure (Pa)
• ρ = density of liquid (kg/m³)
• g = gravitational field strength (N/kg)
• Δh = change in depth (m)

Syllabus: Supplement

4. Energy, Work and Power Formulas

Energy calculations examine how energy is transferred, stored and used. Students should understand work done, power, efficiency and energy changes.

Work Done

Formula:

W = Fd

Where:

• W = work done (J)
• F = force (N)
• d = distance moved in the direction of the force (m)

Work done is equal to the energy transferred.

Syllabus: Core

Kinetic Energy

Formula:

Ek = ½mv²

Where:

• Ek = kinetic energy (J)
• m = mass (kg)
• v = speed (m/s)

Syllabus: Supplement

Gravitational Potential Energy

Formula:

ΔEp = mgΔh

Where:

• ΔEp = change in gravitational potential energy (J)
• m = mass (kg)
• g = gravitational field strength (N/kg)
• Δh = change in height (m)

Syllabus: Supplement

Power

Formula 1:

P = W ÷ t

Formula 2:

P = ΔE ÷ t

Where:

• P = power (W)
• W = work done (J)
• ΔE = energy transferred (J)
• t = time (s)

Syllabus: Core

Efficiency

Percentage efficiency = (Useful energy output ÷ Total energy input) × 100

Percentage efficiency = (Useful power output ÷ Total power input) × 100

Syllabus: Supplement

Efficiency is expressed as a percentage. It cannot exceed 100% for an energy transfer system.

5. Thermal Physics Formulas

Thermal Physics examines how particles behave, how energy is transferred by heating and how temperature affects gases and materials.

Celsius to Kelvin Conversion

Formula:

T (K) = θ (°C) + 273

Where:

• T = temperature in kelvin (K)
• θ = temperature in degrees Celsius (°C)

Syllabus: Core

Gas Pressure and Volume

Formula:

pV = constant

For a fixed mass of gas at constant temperature:

p₁V₁ = p₂V₂

Where:

• p = pressure
• V = volume

Syllabus: Supplement

Specific Heat Capacity

Formula:

c = ΔE ÷ (mΔθ)

Rearranged:

ΔE = mcΔθ

Where:

• c = specific heat capacity (J/kg°C)
• ΔE = thermal energy transferred (J)
• m = mass (kg)
• Δθ = temperature change (°C)

Syllabus: Supplement

6. Waves and Light Formulas

Wave questions require students to understand frequency, wavelength, wave speed, reflection and refraction.

Wave Speed

Formula:

v = fλ

Where:

• v = wave speed (m/s)
• f = frequency (Hz)
• λ = wavelength (m)

Syllabus: Core

Reflection of Light

Relationship:

Angle of incidence = Angle of reflection

Both angles are measured from the normal.

Syllabus: Core

Refractive Index

Formula:

n = sin i ÷ sin r

Where:

• n = refractive index
• i = angle of incidence
• r = angle of refraction

Syllabus: Supplement

The angles must be measured from the normal to the surface.

7. Electricity and Magnetism Formulas

Electrical calculations require students to understand charge, current, potential difference, resistance, electrical energy and power.

Electric Current

Formula:

I = Q ÷ t

Where:

• I = current (A)
• Q = charge (C)
• t = time (s)

Syllabus: Core

Electromotive Force

Formula:

E = W ÷ Q

Where:

• E = electromotive force (V)
• W = electrical work done (J)
• Q = charge (C)

Syllabus: Supplement

Potential Difference

Formula:

V = W ÷ Q

Where:

• V = potential difference (V)
• W = work done (J)
• Q = charge (C)

Syllabus: Supplement

Resistance

Formula:

R = V ÷ I

Where:

• R = resistance (Ω)
• V = potential difference (V)
• I = current (A)

Syllabus: Core

Electrical Power

Formula:

P = IV

Where:

• P = electrical power (W)
• I = current (A)
• V = potential difference (V)

Syllabus: Core

Electrical Energy

Formula:

E = IVt

Where:

• E = electrical energy transferred (J)
• I = current (A)
• V = potential difference (V)
• t = time (s)

Syllabus: Core

Resistors in Parallel

For two resistors connected in parallel:

1/R = 1/R₁ + 1/R₂

Syllabus: Supplement

Potential Divider

Formula:

R₁ ÷ R₂ = V₁ ÷ V₂

Syllabus: Supplement

Transformer Equation

Formula:

Vₚ ÷ Vₛ = Nₚ ÷ Nₛ

Where:

• Vₚ = primary voltage (V)
• Vₛ = secondary voltage (V)
• Nₚ = number of primary turns
• Nₛ = number of secondary turns

Syllabus: Core

For an ideal transformer:

IₚVₚ = IₛVₛ

Syllabus: Supplement

Power Loss in Cables

Formula:

P = I²R

Where:

• P = power loss (W)
• I = current (A)
• R = resistance (Ω)

Syllabus: Supplement

8. Nuclear Physics and Space Physics

Not every topic in the Cambridge Physics syllabus is assessed through a numerical formula. Nuclear Physics includes important definitions and relationships, while Space Physics includes orbital and astronomical calculations.

Radioactive Half-Life

Half-life is the time taken for the number of undecayed nuclei in a radioactive sample, or its activity, to decrease to half its original value.

For repeated half-life calculations:

Remaining quantity = Initial quantity × (½)ⁿ

Where n is the number of half-lives elapsed.

Use this relationship to calculate the remaining quantity after a given number of half-lives.

Orbital Speed

Formula:

v = 2πr ÷ T

Where:

• v = average orbital speed (m/s)
• r = average orbital radius (m)
• T = orbital period (s)

Syllabus: Supplement

Hubble's Law

Formula:

v = H₀d

Where:

• v = speed at which a galaxy is moving away (km/s)
• H₀ = Hubble constant
• d = distance to the galaxy (Mpc)

Syllabus: Supplement

9. Important Physics Units and Symbols

Understanding units is part of applying equations correctly. Use these grouped references when revising calculations.

Motion

• Distance — m (metre)
• Time — s (second)
• Speed — m/s
• Acceleration — m/s²

Forces

• Force — N (newton)
• Mass — kg (kilogram)
• Weight — N (newton)
• Gravitational field strength — N/kg
• Spring constant — N/m
• Momentum — kg m/s

Energy and Thermal Physics

• Work and energy — J (joule)
• Power — W (watt)
• Pressure — Pa (pascal)
• Temperature — K (kelvin) or °C (degree Celsius)
• Specific heat capacity — J/kg°C

Waves

• Frequency — Hz (hertz)
• Wavelength — m (metre)
• Wave speed — m/s

Electricity

• Current — A (ampere)
• Charge — C (coulomb)
• Potential difference — V (volt)
• Resistance — Ω (ohm)
• Electrical power — W (watt)

10. Worked Examples: Applying IGCSE Physics Equations

Use the following examples to see how an equation is selected, values are substituted and the final answer is expressed with the correct unit.

Example 1: Average Speed

A student cycles 240 m in 30 seconds. Calculate the average speed.

Step 1 – Choose the equation

Average speed = Total distance ÷ Total time

Step 2 – Substitute

Average speed = 240 ÷ 30

Answer: 8 m/s

Example 2: Acceleration

A car's velocity increases from 5 m/s to 17 m/s in 4 seconds. Calculate its acceleration.

Step 1 – Choose the equation

a = Δv ÷ Δt

Step 2 – Calculate the change in velocity

Δv = 17 − 5 = 12 m/s

Step 3 – Substitute

a = 12 ÷ 4

Answer: 3 m/s²

Example 3: Hooke's Law

A spring extends by 0.05 m when a force of 2.5 N is applied. Calculate its spring constant.

Step 1 – Choose the equation

k = F ÷ x

Step 2 – Substitute

k = 2.5 ÷ 0.05

Answer: 50 N/m

Example 4: Density

A block has a mass of 800 g and a volume of 200 cm³. Calculate its density.

Step 1 – Choose the equation

ρ = m ÷ V

Step 2 – Substitute

ρ = 800 ÷ 200

Answer: 4 g/cm³

Example 5: Kinetic Energy

A 3 kg object moves at 4 m/s. Calculate its kinetic energy.

Step 1 – Choose the equation

Ek = ½mv²

Step 2 – Substitute

Ek = ½ × 3 × 4²

Ek = 1.5 × 16

Answer: 24 J

Example 6: Wave Speed

A wave has a frequency of 25 Hz and a wavelength of 4 m. Calculate its speed.

Step 1 – Choose the equation

v = fλ

Step 2 – Substitute

v = 25 × 4

Answer: 100 m/s

Example 7: Potential Difference

A component transfers 60 J of energy when 5 C of charge passes through it. Calculate the potential difference.

Step 1 – Choose the equation

V = W ÷ Q

Step 2 – Substitute

V = 60 ÷ 5

Answer: 12 V

Example 8: Electrical Power

A device operates at a potential difference of 12 V and draws a current of 2 A. Calculate its electrical power.

Step 1 – Choose the equation

P = IV

Step 2 – Substitute

P = 12 × 2

Answer: 24 W

11. Common Mistakes in IGCSE Physics Calculations

Knowing an equation does not automatically mean a student can apply it correctly. These are some calculation errors to check during revision.

1. Using Inconsistent Units

Convert measurements before substituting values. For example, convert centimetres to metres when the equation requires SI units.

2. Confusing Mass and Weight

Mass is measured in kilograms. Weight is a force measured in newtons.

3. Forgetting to Square Velocity

Kinetic energy uses the square of velocity. Make sure the entire velocity value is squared before multiplying by mass.

4. Using the Wrong Distance in a Moment Calculation

The moment equation requires the perpendicular distance from the pivot to the line of action of the force.

5. Misreading a Graph

Check the axes before calculating a gradient or area. A speed–time graph and a distance–time graph do not provide the same information.

6. Leaving Out Units

Write the correct unit with every final numerical answer.

7. Rearranging an Equation Incorrectly

Practise making each variable the subject of an equation. This helps when an examination question asks for a different quantity from the one shown in the original formula.

12. How to Revise for IGCSE Physics

A formula becomes useful when a student understands the physical relationship behind it and knows when to apply it.

A structured revision routine can help:

1. Group equations by topic. Revise Motion, Forces, Energy, Waves and Electricity separately.
2. Learn the symbols and units. Know what every letter represents before attempting calculations.
3. Practise rearranging equations. Work out how to find each variable, not only the one shown in the original equation.
4. Solve numerical questions. Apply each equation to different question contexts.
5. Review graph questions. Practise interpreting gradients, areas and relationships between variables.
6. Check Core and Supplement content. Make sure your revision covers the correct examination route.
7. Review mistakes. Identify whether an error came from choosing the wrong equation, converting units or substituting values.

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