Q: What does SEAB O-Level Physics (6091, 2026): The Definitions & Formulae Guide cover? A: A syllabus-faithful, exam-ready list of definitions and relationships explicitly required in Singapore's O-Level Physics (6091, 2026), plus clarifications on common extras.
TL;DR
This is a recall sheet, not a full lesson. Use it to check whether you can state each definition and write each required relationship quickly.
For each formula, learn the quantity meaning, unit, and graph link instead of memorising symbols alone.
If a relationship is not explicitly assessed as a recall/apply formula, this guide labels it so you do not over-memorise.
This post distills the main definitions and formulae that the SEAB O-Level Physics (6091, 2026 syllabus) explicitly expects you to know and apply. Where a concept is commonly taught but not printed as a “recall/apply” relationship in the syllabus, I label it accordingly so you don't memorise more than you need.
Quick recall map
When revising...
Ask yourself...
Definitions
Can I say it in words without using only the formula?
Formulae
Do I know the unit for every symbol?
Graphs
Do I know what the gradient and area mean?
Practical quantities
Do I know what the apparatus actually measures?
Formula-to-meaning checkpoint
Use this four-part check before treating a formula as memorised. It keeps recall tied to the physics, not just to symbol matching.
Treating the same letter as the same physical quantity in every topic.
Unit check
Give the SI unit for the final answer and for the substituted values.
Getting a correct-looking number with incompatible units.
Graph link
Name the graph gradient, area, or intercept if the relationship has one.
Memorising the equation but missing the graph question.
Practical link
Name the instrument or observation that would produce the data.
Forgetting that formula questions often come from experiments.
Worked check: for p=F/A, do not only say "pressure equals force divided by area". A stronger recall sentence is: pressure is force per unit area; force is measured in newtons, area in square metres, and pressure in pascals; if the same force acts over a smaller contact area, pressure increases.
Misconception check: a definition is not just the formula written in words. It should name the physical idea that the formula is measuring.
Concrete example: speed is not just a formula
Weak recall:
Speed equals distance divided by time.
Better recall:
Speed is the rate of change of distance. Its SI unit is metre per second. On a distance-time graph, the gradient gives speed.
The second version is exam-safer because it links the definition, unit, and graph interpretation in one answer.
Stay Connected
Use our O-Level Physics Experiments hub to keep formula drills synced with the hands-on investigations you'll meet in Paper 3.
At-a-glance formula sheet
Units are SI unless stated. Use the value of g given in the question. If none is given, follow your school’s convention (many schools use g=10ms−2 for simpler arithmetic; some use g=9.81ms−2).
Measurement & basics
No explicit equations beyond rearrangement and graphing in the form y=mx+c.
Kinematics
Average speed:vˉ=timedistance
Acceleration:a=ΔtΔv
Graph facts: area under a velocity-time graph = displacement; gradient of a velocity-time graph = acceleration.
Dynamics
Weight:W=mg
Resultant force (Newton's 2nd law form):F=ma
Turning effects
Moment (torque):τ=Fd⊥ (perpendicular distance to pivot)
Principle of moments (equilibrium): sum of clockwise moments = sum of anticlockwise moments
Pressure & density
Pressure (mechanical):p=AF
Density:ρ=Vm
Hydrostatic pressure:p=hρg
Energy, work & power
Work done:W=Fsforce×displacementalongthelineofaction
Kinetic energy:Ek=21mv2
Gravitational potential energy (near Earth):Ep=mgh
Power:P=tE
Efficiency:efficiency=total inputuseful output
Thermal physics
Specific heat capacity:Q=mcΔT
Specific latent heat:Q=mL
Waves
Wave speed:v=fλ
Light
Reflection: angle of incidence = angle of reflection
Refraction (Snell's-law form in 6091):sinrsini=constant
Refractive index (definition-based):n=vc (speed in vacuum over speed in medium)
Electricity (current & circuits)
Charge:Q=It
Resistance (defining relation):R=IV
Series circuits:Rseries=R1+R2+⋯
Parallel circuits:Rparallel1=R11+R21+⋯
Practical electricity
Electrical power:P=VI
Electrical energy (constant V and I):E=VIt
Billing (kWh):E(kWh)=P(kW)×t(h)
Cost = energy (kWh) x tariff
Magnetism & electromagnetism
No new equations (qualitative field patterns, force directions, etc.)
Critical angle and total internal reflection (concepts).
Image characteristics for a thin converging lens: real/virtual, upright/inverted, magnified/diminished; draw and interpret ray diagrams.
Focal length of a converging lens (concept/use).
Electricity
Electric field: region where a charge experiences a force.
Current: rate of flow of charge A.
Electromotive force (e.m.f.): work done per unit charge by the source around a complete circuit V.
Potential difference (p.d.): work done per unit charge across a component V.
Practical electricity (safety)
Live, neutral, earth (ground) wires: meanings and roles.
Mains plug wiring; switches/fuses on the live wire; earthing and double insulation.
Magnetism & electromagnetism
Magnetic field (field lines and patterns around magnets, straight conductors, and solenoids).
Electromagnetic induction
Qualitative induction (what changes increase induced e.m.f., sketching AC output).
(Mnemonic names like “Fleming's right-hand rule” are not required by the spec, though left-hand rule is commonly discussed for motors.)
Radioactivity
Nuclide notation ZAX (interpret A,Z).
Alpha, beta, gamma: nature and effects on A and Z.
Half-life (meaning and use in simple calculations).
Nuclear fission and fusion (meanings).
Activity A (symbol/unit recognition; formal A=λN not required).
Practice Quiz
Check your memory of must-know definitions and equations-while spotting the "common extras" you can deprioritise.
Worked “formats” you will actually use
1) Hydraulics / fluids
p=AF and p=hρg appear often in connected-container or manometer contexts.
2) Energy chains & power
Combine P=VI with E=VIt to move between power, current, voltage, time, and energy.
Billing: convert W ↔ kW and s ↔ h cleanly before multiplying by the tariff.
3) Graphing to linear form
Many lab relationships need rearrangement to y=mx+c so that the gradient/intercept equals a physical constant. Label axes with units and propagate uncertainties sensibly.
4) Lens work
Use ray diagrams for object>f, =f, and <f. Quote image properties rather than plugging a magnification formula (not required).
5) Radioactive decay questions
Balance nuclide equations for α and β (β−) increases Z by 1, A unchanged; α decreases A by 4 and Z by 2; γ leaves A,Z unchanged.
Half-life: read off from tables/curves or apply stepwise halving; avoid introducing λ unless given.
“We added these after review”
From our discussion, these are part of 6091 and worth putting on your sheet:
Internal energy (definition).
Terminal velocity (concept under motion with air resistance).
Electrical energy & cost in kWh (plus P=VI, E=VIt).
Nuclide equations for α, β, γ and half-life calculations.
Commonly taught but not printed as recallable relations in 6091
You may still learn/use these in class, but they're not listed as formulae to memorise in this syllabus:
f=T1 (frequency-period)
Critical angle formula:sinc=n1
Magnification and thin-lens equation f1=u1+v1
Average velocity = displacement/time (only average speed is printed)
ResistivityR=ρAℓ
Radioactive decay lawN=N0(21)t/T1/2
Named mnemonics like right-hand grip and Fleming's right-hand rule (qualitative ideas are examined, but the mnemonics themselves aren't specified)
Final notes
Stick to SI units and clear significant figures.
When in doubt, draw the diagram (free-body, ray, circuit, field lines) and map each quantity to the appropriate relationship.
The syllabus emphasises interpretation of graphs, proportional reasoning, and linking concepts (e.g., energy → power → cost), as much as raw formula recall.
If you'd like this turned into a printable A4 one-page reference PDF (with units and a small index), I can generate it now.
