Inquiring and designing
🎯The four strands
At Year 5 the strands ask you to:
- i. Explain a problem or question to be tested by a scientific investigation.
- ii. Formulate a testable hypothesis and explain it using scientific reasoning.
- iii. Explain how to manipulate the variables, and explain how sufficient, relevant data will be collected.
- iv. Design a logical, complete and safe method, selecting appropriate materials and equipment.
📊The three kinds of variable — the heart of it
Almost every mark in criterion B depends on handling variables cleanly. There are exactly three roles:
- The independent variable — the one thing you deliberately change.
- The dependent variable — the one thing you measure in response.
- The controlled variables — everything else you must keep the same, so that any change you see can only be due to the independent variable.
A fair test changes one thing and holds the rest still. Naming the controlled variables — and saying how you will hold each one constant — is the difference between a middling and a top-band design.
📈What moves you up the bands
A 1–2 design states a hypothesis and lists some equipment. A 7–8 design gives a hypothesis with a reason grounded in physics, identifies all three kinds of variable, explains how each controlled variable will actually be kept constant, chooses instruments whose precision suits the measurement, and plans enough repeats and enough spread of readings to see a real pattern. The recurring word is explain: not “keep the mass the same” but “use the same trolley throughout so its mass, 0.50 kg, does not change between runs”.
✏️A worked design
Hypothesis, with reasoning: As the length increases, the period will increase. A longer pendulum has a smaller restoring acceleration for a given displacement, so it takes longer to complete each swing; I expect the period to rise with length, and (from the theory of simple harmonic motion) to depend on the square root of length rather than on length directly.
Variables: Independent — the length of the string, changed in six steps from 0.20 m to 1.20 m. Dependent — the period, found by timing ten swings and dividing by ten. Controlled — the mass of the bob (same bob throughout), the release angle (kept below 10°, measured with a protractor, so the motion stays simple-harmonic), and the same stopwatch and operator to keep timing consistent.
Data collection: At each length, time ten complete swings and repeat three times, so anomalies show up and a mean can be taken. Timing ten swings rather than one divides the human reaction-time error by ten. Six lengths across a wide range give enough points to see the shape of the relationship, not just two points that could be joined by any curve.
Safety and equipment: Clamp the stand to the bench so it cannot topple; keep feet clear of the swinging bob. A metre rule reading to a millimetre suits the length; a stopwatch reading to 0.01 s suits the time.