Fukuoka Entrance Science common mistakes
Fukuoka Entrance Science · Understand the traps and how to avoid them.
When asked to find the net force or acceleration, the candidate plugs the given force straight into F = ma without first drawing a free-body diagram, so they forget to add or subtract the friction force, the normal force, or gravity's component along the slope.
The candidate has memorised F = ma as a formula to substitute numbers into, and they skip the step of identifying which forces act and in which direction. Word problems that mention only one force encourage this shortcut, and it then fails on slopes, pulleys, and surfaces with friction.
What to do instead
Before substituting any numbers, draw a free-body diagram and label every force with its direction. Resolve forces along and perpendicular to the motion, then write the net force as a sum with signs. Practise problems with friction on a slope and with two connected bodies until drawing the diagram becomes automatic.
The candidate treats energy and force as interchangeable, answering 'the energy of the ball increases' when only its kinetic energy changes, or confusing work with power and stating that a machine does more work because it is more powerful.
Everyday language uses 'force', 'energy', and 'power' loosely, and the textbook definitions are close together. The candidate has not separated the quantities by their units or by what they physically measure.
What to do instead
Build a one-page table listing each quantity with its symbol, unit, and defining equation (work = force × distance, power = work ÷ time, kinetic energy = ½mv²). For every problem, write the unit next to the answer and check it against the quantity asked for. Redo missed problems by naming the quantity before calculating.
The candidate draws or predicts a circuit using the wrong rule, for example assuming current is used up as it passes through each resistor, or adding resistances in parallel by simple addition, so the calculated current or voltage is wrong.
The candidate memorises series and parallel rules as lists without a mental model of charge flow. The idea that current 'gets consumed' feels intuitive, and parallel resistance formulas are applied without checking whether the branches share voltage or current.
What to do instead
State the governing principle first: current is conserved at junctions, and voltage is shared in series but equal across parallel branches. For each circuit, mark the current at every point and the voltage across every element before calculating. Verify with Ohm's law at each element and check that the total current equals the sum of branch currents.
The candidate confuses wave speed, frequency, and wavelength, believing that a wave entering a denser medium speeds up and its frequency rises, or mixing up the relationship v = fλ when the medium changes.
Frequency feels like it should change with the medium because the wave 'feels' different, and the three quantities are introduced together. The candidate has not learned that frequency is set by the source and only speed and wavelength change at a boundary.
What to do instead
Anchor the rule: the source fixes frequency, so f is constant across a boundary; v changes with the medium, and λ = v/f changes with it. Practise refraction of water waves and sound entering a different medium, calculating λ before and after. State explicitly which quantity is fixed by the source in each answer.
The candidate answers a light or mirror/lens question by describing the image from memory ('virtual, upright, magnified') without determining the image position from the ray diagram or the lens equation, so the description contradicts the given object distance.
The candidate has memorised image descriptions for a few standard cases and applies them regardless of the actual object distance. They do not check whether the object is inside or outside the focal length.
What to do instead
Always locate the image first: draw two or three principal rays to find where they meet or appear to meet, then read off whether the image is real or virtual and upright or inverted. Compare the object distance with the focal length before writing any description. Use the lens equation as a numerical check when values are given.
The candidate classifies a substance as a mixture or a pure substance from its appearance alone, calling salt water a pure substance because it looks clear, or calling a compound a mixture because it contains two elements.
The candidate relies on visual cues rather than on the definition of a pure substance (fixed composition, single substance) and has not distinguished compounds from mixtures by whether components can be separated by physical means.
What to do instead
Apply the test in order: can the components be separated by physical means such as filtration or distillation? If yes, it is a mixture; if it requires a chemical change to break down, it is a compound. Classify a set of examples (air, seawater, pure water, carbon dioxide, brass) and justify each with the separation method.
The candidate balances a chemical equation by changing subscripts in a formula, for example turning H2O into H2O2 to make oxygen atoms balance, instead of adjusting coefficients in front of the formulas.
The candidate treats balancing as an arithmetic puzzle and does not understand that changing a subscript changes the substance. The habit forms when the first attempt does not balance and the quickest-looking fix is a subscript change.
What to do instead
State the rule explicitly: subscripts are fixed by the substance and only coefficients may change. Balance by inspection in a fixed order (metals, non-metals, hydrogen, oxygen), then recount every element on both sides. Check by naming each substance after balancing to confirm the formulas are unchanged.
The candidate confuses the roles of the plant and animal in reproduction, saying the pollen is the male gamete that travels to the ovule, or stating that seeds form without fertilisation, and mixing up the functions of the stamen, pistil, and ovary.
The candidate learns the parts of a flower as a list of labels without the sequence of events. Terms such as 'pollen' and 'gamete' are not connected to the process of pollination, fertilisation, and seed formation.
What to do instead
Write the process as an ordered chain: pollination (transfer of pollen) → pollen tube grows → fertilisation of the ovule → seed and fruit form. Draw and label a flower and trace the path of the pollen tube. Practise answering questions that ask specifically about one stage, and name the stage in the answer.
The candidate explains heredity by saying that traits are inherited from whichever parent the child resembles, or that dominant traits are the ones that appear most often in the population, rather than distinguishing genotype from phenotype and dominant from recessive alleles.
The candidate uses the everyday meaning of 'dominant' (most common) instead of the genetic meaning (expressed when one copy is present). The distinction between the alleles an organism carries and the trait it shows is not made explicit.
What to do instead
Define genotype as the allele pair and phenotype as the observable trait, and define dominant as the allele expressed in a heterozygote. Use Punnett squares with clear allele symbols and report both genotype and phenotype ratios. Work through a cross where a recessive trait appears in offspring of two dominant parents to show the distinction.
The candidate answers Earth and space questions by reciting a fact in the wrong context, for example saying stars are made of burning gas like a fire, or that the seasons are caused by Earth's changing distance from the Sun, or that the Moon's phases are caused by Earth's shadow.
These explanations are intuitive and reinforced by everyday language ('the Sun burns'). The candidate has not connected the observation to the correct mechanism, such as axial tilt for seasons and orbital position for phases.
What to do instead
For each phenomenon, state the mechanism and the evidence: seasons come from the constant tilt of Earth's axis changing the angle of sunlight; lunar phases come from the changing angle between Earth, Moon, and Sun; stars shine by nuclear fusion in their cores. Draw a diagram for each and explain a common misconception and why it is wrong.