Download clean, printable lists of the most common mistakes students make — so you can fix them before they cost marks.
Each sheet is aligned to its exam board and built from recurring student errors highlighted in examiner reports and mark schemes.
What you get
A topic-by-topic mistakes list with a “do this instead” fix and a quick self-check.
How to use it
Review before past papers, then use the quick checks to catch errors under timed conditions.
Why it works
Many marks are lost on predictable slips: rounding, sign errors, units, and misreading commands.
Coverage by topic
Preview (up to 5 per topic)
20 total rows in download
| Topic | Common mistake / misconception | Do this instead | Quick check |
|---|---|---|---|
| Measurements | Confusing precision and accuracy. | Accurate = close to true value. Precise = repeated measurements close together. You can be precise but inaccurate (systematic error). | Systematic error affects accuracy. Random error affects precision. |
| Measurements | Not showing units throughout calculations. | Every step of a calculation must carry units. Cancel units correctly — this helps catch errors and is required in Cambridge mark schemes. | Are units shown at every step, not just the final answer? |
| Measurements | Quoting answers to too many significant figures. | Match sig figs to the data given (usually 2–3). Cambridge mark schemes penalise over- or under-rounding. | Fewest sig figs in the data? Round your answer to match. |
| Kinematics | Using suvat equations when acceleration is not constant. | Suvat (v=u+at etc.) ONLY apply for constant/uniform acceleration. For variable acceleration, use calculus or graphs. | Is acceleration constant? If not, suvat cannot be used. |
| Kinematics | Forgetting that displacement and velocity are vectors — sign matters. | Define a positive direction. Displacement going back is negative. Velocity decreasing must be shown with correct sign in suvat. | Did you define a positive direction and stick to it? |
| Forces | Confusing mass and weight in calculations. | Mass = kg (scalar). Weight = N (force, vector). W = mg. Never write 'weight = kg' or use 10 kg when you mean 100 N. | Does your equation use kg or N? Mass in kg; weight/force in N. |
| Forces | Missing forces when drawing free body diagrams. | Check for all forces: gravity (mg), normal reaction, friction, tension, air resistance, applied force. Draw separately from surroundings. | Newton's 3rd law pairs? Applied forces? Friction direction? |
| Forces | Taking moments about the wrong point. | Take moments about a point where an unknown force acts — it eliminates that unknown from the equation and simplifies solving. | Take moments about the point where you want to cancel an unknown force. |
| Energy | Saying energy is 'lost' in a system. | Energy is never lost — it is TRANSFERRED to other forms (usually thermal/heat). Conservation of energy always holds. | Replace 'energy is lost' with 'energy is transferred to thermal energy'. |
| Energy | Confusing power and energy. | Energy = amount of work done or heat transferred (J). Power = RATE of energy transfer (W = J/s). P = W/t = Fv. | Power is energy per unit time. P = E/t or P = Fv. |
| Waves | Saying light is a longitudinal wave. | Light (and all EM waves) are TRANSVERSE — oscillations perpendicular to direction of travel. Sound is longitudinal. | EM waves = transverse. Sound = longitudinal. |
| Waves | Confusing frequency and wavelength relationship when wave speed changes. | v = fλ. When wave enters a new medium, frequency stays CONSTANT, speed and wavelength change. f is fixed by the source. | Wave slows in denser medium → wavelength decreases; frequency unchanged. |
| Waves | Drawing interference patterns without explaining path difference. | Constructive: path difference = nλ. Destructive: path difference = (n + ½)λ. Must link fringe position to path difference. | State the path difference condition for constructive vs destructive interference. |
| Electricity | Confusing EMF and terminal voltage. | EMF = total energy per unit charge supplied by source. Terminal voltage = EMF − voltage drop across internal resistance. V = E − Ir. | Terminal voltage < EMF always (when current flows). V = E - Ir. |
| Electricity | Saying resistance of a wire decreases when it gets longer. | R = ρL/A. Resistance INCREASES with length. Doubling length doubles resistance (at constant cross-section and temperature). | R ∝ L (directly proportional). Longer wire = more resistance. |
| Electricity | Forgetting internal resistance in circuit calculations. | Real batteries have internal resistance r. Total EMF drives current through (R + r). Terminal PD = E − Ir. | Is there a 'real battery' in the question? Check for internal resistance. |
| Fields | Confusing gravitational and electric field direction conventions. | Gravitational field lines point TOWARDS mass (always attractive). Electric field lines point away from +ve charge, towards −ve charge. | Gravity: always attractive, fields point inward. Electric: direction depends on charge sign. |
| Fields | Applying Coulomb's law to non-point charges without justification. | Coulomb's and Newton's inverse-square laws apply to POINT charges/masses, or spherical ones treated as points. State this assumption. | Are the objects much smaller than their separation? If so, point-charge approximation is valid. |
| Nuclear Physics | Confusing mass number and proton number in decay equations. | Mass number (top): must balance on both sides. Proton number (bottom): must also balance. Check BOTH separately. | Balance top numbers separately from bottom numbers in nuclear equations. |
| Nuclear Physics | Saying radioactive decay is predictable for individual nuclei. | Decay is RANDOM for individual nuclei. Half-life describes STATISTICAL behaviour of large numbers — not when any one nucleus will decay. | Individual nucleus: random. Large sample: predictable half-life statistics. |