NCEA L1 Physics & ESS common mistakes
NCEA L1 Physics & ESS · Understand the traps and how to avoid them.
Writing the answer with no unit, or writing the unit after squaring or dividing (e.g. giving speed in 'm' or energy in 'N').
Candidates copy the number from the calculator display and treat the unit as decoration, so they never check that the unit matches the quantity actually asked for.
What to do instead
After every calculation, name the quantity in words first ('this is a speed, so metres per second'), then write the unit symbol. Practise by covering the units in past-paper answers and predicting them before checking.
Substituting numbers into a formula before rearranging it, then losing track of which variable is the subject.
Rearranging under time pressure feels risky, so candidates plug in early and then try to 'undo' the arithmetic, which produces inverted equations such as v = d/t written as t = v/d.
What to do instead
Rearrange symbolically first, write the rearranged line on its own, and only then substitute. Check by dimensional reasoning: if the rearranged expression would give time in m/s, it is wrong.
Treating a vector quantity as a scalar, e.g. adding speeds 3 m/s and 4 m/s and stating the resultant velocity is 7 m/s regardless of direction.
Candidates learn 'add the numbers' from scalar work on mass and energy and do not register that direction changes the arithmetic.
What to do instead
Before adding any quantity, ask 'does direction matter here?' If yes, draw a labelled arrow diagram or triangle and use Pythagoras or a scale drawing; state the direction in the answer.
Reading a distance–time graph as if it were a speed–time graph, so a horizontal line is described as 'stopped' when it actually means constant speed.
Both graphs look identical in shape, and candidates match the shape to a memorised story rather than reading the axis labels.
What to do instead
Cover the graph, read the vertical axis label aloud, and write its unit at the top of the working. Then translate each segment into words using that unit before answering.
Describing an energy transfer as 'energy is used up' or 'energy is lost' rather than identifying where it went.
Everyday language treats energy as a fuel that is consumed, and candidates repeat that phrasing instead of naming the transformation.
What to do instead
For every energy question, write the chain 'from X store to Y store' (e.g. gravitational potential to kinetic plus heat by friction) and state that total energy is conserved.
Giving a description of an observation when the question asks for an explanation, e.g. 'the bulb got brighter' with no reference to resistance or current.
Candidates answer the question they can see in the diagram rather than the command word in the prompt, and 'explain' questions carry most of the marks.
What to do instead
Underline the command word (describe, explain, justify, calculate) before writing. For 'explain', force yourself to include a because-clause linking two named physics ideas.
Confusing the three rock types and describing the rock cycle as a one-way sequence rather than a set of looping processes.
The cycle is taught as a diagram with arrows, and candidates memorise arrow order without linking each arrow to a process such as melting, cooling, or compaction.
What to do instead
Learn each transition as a process-plus-product pair: 'heat and pressure on any rock gives metamorphic', 'cooling magma gives igneous with crystals'. Draw the cycle from memory and label every arrow with its process.
Explaining tectonic plate movement by saying 'the plates float on the mantle' or that 'heat makes them rise' without naming convection or slab pull.
Candidates mix the everyday idea of floating with the actual mechanism and stop at a vague heat statement.
What to do instead
Use the causal chain: heat from radioactive decay and residual heat drives convection in the mantle, which drags plates at the base; dense subducting slabs also pull plates down (slab pull). Write the chain in full for one example such as the Pacific Plate.
Mixing up the order of the Solar System, or the relative sizes and distances of planets, Sun and nearest stars, when asked to compare.
Scale is counter-intuitive: diagrams in textbooks are not to scale, so candidates underestimate how empty space is and how small planets are relative to the Sun.
What to do instead
Memorise the order with a mnemonic, then anchor a few real figures (light from the Sun takes about 8 minutes; the next star is over 4 light-years away) and use ratios rather than absolute guesses when comparing.
Answering an Earth and Space Science question about evidence with an opinion or a single data point, e.g. 'the climate is changing because it was hot last summer'.
Candidates do not distinguish between a claim and the evidence that supports it, and they treat personal experience as data.
What to do instead
Use the pattern 'claim - evidence - reasoning': state the pattern seen in long-term data (e.g. decades of temperature records, ice-core CO2), then explain why that data supports the claim. Reject single events as evidence in your own writing.