Why Physics is reasoning-chain heavy
Pure Physics OEQs typically present a scenario (a moving object, a circuit, a wave, an EM situation) and ask the student to explain a behaviour. The mark scheme rewards a short sequence of cause → effect steps, each grounded in a named physical principle (Newton's laws, conservation of energy, conservation of momentum, Ohm's law, etc.).
A correct answer is rarely longer than 4-6 lines but every line should advance the chain.
The Physics CER pattern
Physics CER usually compresses to:
- Claim — what happens to the object/system.
- Evidence — what force, current, field, or wave is acting on it, drawn or named.
- Reasoning — the principle being invoked (named explicitly), and the cause-effect step.
When to draw a free-body diagram (FBD)
For Mechanics OEQs, an FBD almost always earns marks even if not explicitly asked for:
- Object on an incline → show weight, normal force, friction.
- Object in lift → show weight and tension/normal.
- Object in circular motion → show centripetal force direction.
- Connected objects (rope, pulley) → separate FBDs per object.
FBDs lose marks when forces are unlabelled, missing, or drawn from the wrong point of application.
Worked example
Question (3 marks): "A car of mass 1200 kg accelerates uniformly from rest to 20 m/s in 8 seconds. Explain how Newton's Second Law relates to the forward force on the car."
Strong answer:
- Acceleration: a = (v − u) / t = (20 − 0) / 8 = 2.5 m/s² [1]
- Newton's Second Law: F = ma [1]
- Substitution: F = 1200 × 2.5 = 3000 N. The forward (resultant) force is 3000 N [1].
Three marks, three steps, principle named, calculation shown.
Topic-by-topic Physics OEQ tips
- Kinematics & Dynamics — quote the equation, do the substitution, state the unit. Always.
- Energy — name "kinetic energy", "gravitational potential energy", "elastic potential energy", "principle of conservation of energy" explicitly.
- Pressure & Density — write P = F/A or ρ = m/V before substituting. Cite which formula applies.
- Thermal — distinguish heat (energy transferred) from temperature (measure of average KE). Mark schemes catch confusion here.
- Electricity — V = IR explicitly. Resistors in series add; resistors in parallel use the reciprocal formula. State which combination applies.
- EM induction — name "Faraday's law" and the direction of induced current per Lenz's law. These are mark-bearing keywords.
- Waves — v = fλ; distinguish transverse vs longitudinal; state the medium properties when relevant.
Common Physics OEQ mark traps
- Forgetting units. "F = 3000" without "N" can lose a mark.
- Vague principle. "Because of physics" instead of "by Newton's Second Law, F = ma".
- Direction without specifying. "Force acts on the object" is incomplete. State direction relative to a defined axis or reference.
- Skipping the formula line. Going straight from "given m and a" to "F = 3000 N" loses the method mark.
- FBD with hidden forces. Forgetting friction on an incline, or air resistance when the question explicitly mentions it.
How to drill Physics OEQ
Build a single sheet of the ~20 most-used Physics principles + formulas. Practice writing each in the form "Name → equation → typical use case". Then take past-paper OEQs and answer them by first identifying which principle applies, naming it, writing the equation, then substituting.
For the underlying answer structure used across Bio/Chem/Phys, see CER structure. For Biology OEQ (different rhythm — heavier on keywords), see Biology OEQ keywords + structure. For broader OEQ technique, see the pillar how to score better on open-ended questions for G3 Science.
Whose method this is. The syllabus content is set by SEAB — this page is checked against the G3 Physics syllabus (K323) for the 2027 SEC. The formula-then-reasoning structure taught here is Genie's own. It is not a national requirement, and no exam board mandates it. Last reviewed 16 Aug 2026.