92045 · Investigating a physical phenomenon

• Four different things in one investigation

  A falling muffin case is the phenomenon: you can watch it happen. Air resistance (the drag of the air on the moving case) and gravitational potential energy (the energy the case has because of its height above the tray) are concepts — ideas, not numbers. Release height in centimetres and fall time in seconds are quantities. “As height increases, fall time increases” is the relationship: a connection you can observe between those two numbers. Students mix the four. Calling refraction a quantity, current a phenomenon, or “a falling object” a relationship leaves the plan with nothing numerical to test. Sort the four before you write a method.

• A usable phenomenon can carry two relationships

  “Does a parachute work?” is one qualitative question. Release height against fall time, and canopy area against fall time, are two numerical connections in the same falling-object phenomenon. Moderation looks for a phenomenon that can carry at least two such relationships, explained with at least two relevant physics concepts. That expectation sits in moderator reports, not in the standard’s own explanatory notes, so do not quote it as if the standard listed a number. Use it as a planning test: if you cannot name two concepts and two quantity-pairs, the phenomenon is too thin. The concept list that appears in those reports — gravitational potential energy, kinetic energy, conservation of energy, air resistance, friction, voltage, current, conduction, convection, radiation — is usable context, not a closed syllabus.

• A focusing question names two quantities

  A focusing question names the two quantities whose connection the investigation will test, in a form that can produce numerical evidence. “How does canopy area in square centimetres affect fall time in seconds?” does that. “How does the colour of the paper affect the drop?” names a quality. “I will do a fair test with a muffin case” names a method. “What is the best parachute?” names a preference. If you cannot write both quantities with a unit, you do not yet have a focusing question. The question is the plan’s hinge: everything else — range, controls, the second relationship — has to serve those two numbers.

• Independent, dependent and controlled quantities

  The independent quantity is the numerically ordered physical quantity you deliberately change: 40 cm, 80 cm, 120 cm of release height, not “low / medium / high”. The dependent quantity is the numerical quantity you measure to see how it responds: fall time in seconds. A controlled quantity is a physical factor held steady because it would change this measured relationship if it were free to vary — canopy area, mass, and still air for a height–time test. The control exists so the physics relationship stays numerical. It is not there so someone can grade the method. Do not dress the same map up as reliability or validity: those words belong to a different standard.

• Categories have to become ordered numbers

  A quality such as the surface a ball rolls along is difficult to put into the equation of a relationship. Carpet versus wood, black paper versus white, or “with a parachute / without one” will not sit on numerically ordered axes, and a conclusion cannot then say how the dependent quantity increased or decreased when the independent quantity changed in magnitude. Repair the draft. Surface material becomes thickness in millimetres, or a measured roughness, or a friction coefficient if you actually measure one. Colour becomes percentage black coverage. With or without a canopy becomes canopy area from zero upwards. Insulation that is only “wool versus foil” becomes thickness of the wrapping, or a stated R-value. The number is what the relationship needs.

• Three official routes to a second relationship

  A second relationship is a distinct numerical connection in the same phenomenon, not a repeat of the first test with a tidier method. There are three official routes. Run two fair-test investigations that each give evidence of the phenomenon — height against time, then area against time. Or take a quantity you controlled in the first relationship and investigate it as a second numerical independent quantity — the paperclip mass you held constant now becomes the thing you change. Or find a lower or upper limit of the first relationship and investigate that further — a rotor so short the craft tumbles instead of spinning. More repeats, a different stopwatch, or the same two quantities written up more neatly are not a second relationship.

• A pilot chooses range, not a finished dataset

  Processed evidence is data you have synthesised — a table, a graph or a calculation — so the relationship is clearer than in the raw readings. Merit has to use that kind of evidence to explain how concepts and relationships are involved. On this page a short processed pilot is something you are given, so you can choose a range, an interval, a resolution, or a second relationship. If times at 20 cm and 40 cm look the same on a 0.01 s stopwatch, the interval is too small or the drop is too short. If at 180 cm the case clips a cupboard, the range is unusable. If a very short canopy starts to tumble rather than fall steadily, that limit can become a second relationship. How to compute a mean, fit a line or take a gradient is the next page’s job.

• Safety and feasibility stay inside the physics

  A safety limit belongs in the plan when it would wreck the measurement or the student. Catching a falling case by hand adds an unmeasured force, so the fall time is no longer the time the relationship asked for; use a tray. Climbing on a desk for extra height adds an unmeasured extra drop and a fall risk; keep the stand on the floor. A current-limited pack and a cooling interval matter because a coil or filament that overheats changes resistance, so the voltage–current relationship you came to see is no longer the one you are measuring. Water held below about 60 °C is both a burn limit and a control that can actually be held. Bright sources sit below eye level. Low-voltage supplies, light objects, padded stops and secured stands are physics-specific reasons, not a generic laboratory poster.

• Bright, dim and off are not yet quantities

  “Bright / dim / off” will not sit on a numerically ordered axis. Neither will “LED versus filament versus halogen”. Those are categories. Repair them: change the pack in volts, or the current in amperes; measure illuminance in lux, or use a stated filament rating in watts as a number if that number is supplied. Coding the three lamp types as 1, 2 and 3 does not measure them. A bar chart of lamp names is the same error drawn as a picture. The independent quantity has to be a number you can put in order so a conclusion can say how the dependent quantity increased or decreased in magnitude.

• A lamp still needs a second numerical relationship

  A lamp can carry two distinct numerical relationships. Voltage against current is one. Illuminance against voltage, or illuminance against the distance of the meter, is another. The three official routes still apply: run two fair-test pairs (V against I, then covering-percentage against lux); promote a former control (meter distance was held at 25 cm, now you change it); or investigate a limit (below some voltage the filament does not glow, so the V–lux connection no longer looks like the glowing region). More repeats of the same V–I pair are not a second relationship. A short constructed pilot chooses range — 1.0 V may not light this globe; 7.0 V may overheat it. The pilot is not the internal, and Whetū is not grading a lab you ran.

Internal · marked per part.

This is an internal achievement standard. Whetū does not offer a sit-down Exam paper for it. Learn and Practise stay available.

2 authored Learn units for this standard.

• Planning an investigation

  This page is about planning an investigation of a physical phenomenon: an observable event that involves physics ideas. A muffin case falling from a stand, a low-voltage lamp changing brightness, or light spreading through a prism can all work. The investigation is only the vehicle. What is assessed is the physics those measurements illustrate, not a tidy method, a risk table, or the words “fair test”.

• Processing and representing data

  A list of stopwatch readings is evidence, but it is not yet processed evidence. This page is about the next move: turning those numbers into a representative mean, a table that keeps the raw columns beside the processed ones, a graph on numerically ordered axes, a line of best fit, a gradient with units, or a calculation that says something the raw list does not. The achievement standard’s own wording is that processed evidence is evidence you have synthesised so that it gives more meaningful information. The official examples are calculations, tables and graphs.

36 Practise questions in “Investigating a physical phenomenon”. Feedback here is formative and is not an official NCEA grade.

• A usable phenomenon

  A phenomenon that can carry two numerical relationships.

• Independent, dependent, controlled

  Name the three roles. Categories must become ordered numbers.

• Focusing question

  The question names two quantities.

• A second relationship

  The three official routes. Pilot chooses range, not a finished dataset.

• Processed evidence

  Synthesised, not copied. A mean is processed; an anomaly is investigated.

• Graphs and gradient

  A relationship graph, not categories. Line of best fit carries a gradient with units.

• Interpolation and extrapolation

  Inside the range versus outside it.

• Describe, then explain

  Compare magnitudes, then explain with the processed numbers.

Sample questions

1. Which classroom event is a usable physical phenomenon for this standard — one that can carry two numerical relationships?
2. A paper spinner falls from a retort stand. Match each term to the part of that investigation it names.
3. Which student has sorted the four correctly?
4. A group’s whole plan is: “Does a paper spinner work?” Why is that phenomenon too thin for this standard?
5. Which quantity is independent in this plan?
6. A trolley runs down a ramp. Match each role to the quantity that fills it in this plan.
7. What is wrong with treating those 1–2–3 codes as the independent quantity?
8. This plan treats a quality as the independent quantity and borrows words from another standard. Which changes would repair it for 92045? Select all that apply.

Practise 92045 in Whetū