Investigation planning and methods
- Syllabus
- 2024
- Topic
- —
- Level
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Learning objectives
—Devise and plan investigationsDevise and plan investigations, using scientific knowledge and understanding when selecting appropriate techniques.—Safe and appropriate experimental methodsDemonstrate or describe appropriate experimental and investigative methods, including safe and skilful practical techniques.
Plan an investigation from the physics relationship
A useful investigation plan turns a physics relationship into a repeatable comparison. It states what will be changed, what will be measured, what must stay constant and which technique will produce the required measurement.
Plan in this order: define the relationship to investigate → choose a sensible range and several values for the quantity changed → select apparatus that measures the response → identify conditions that could also affect the response and keep them constant → describe how each reading is taken → repeat readings and calculate a mean when repetition is appropriate.
Example: to investigate how magnetic field strength changes with distance from a coil, use a ruler to set several distances and a Hall probe to measure field strength at each position. Distance is changed, field strength is measured, and current plus coil geometry are kept constant. Repeating each field reading and finding a mean makes the comparison more dependable.
An apparatus list is not a complete plan. Each item must have a stated purpose, and the procedure must reveal how the selected technique tests the physics relationship. Changing several relevant conditions together would make the cause of any measured change unclear.
Choose a safe method that measures the intended quantity
An appropriate experimental method uses apparatus that measures the intended physical quantity and a technique that produces meaningful readings without exposing people to an avoidable hazard.
| Measurement task | Appropriate method | Essential technique |
|---|---|---|
| mass of an object or container | balance | zero the balance, then record mass in its stated unit |
| weight or another force | newton meter | check the zero and read the scale in newtons while the force acts along the meter |
| corrected radioactive count rate | GM tube with counter and timer | measure background count several times, calculate its mean, then subtract the mean background from the source reading |
Safety must follow the chain hazard → possible harm → control. Liquid nitrogen can cause harm through extreme cold and splashing, so use eye protection and suitable protective gloves and pour carefully to avoid splashes. The control must match the actual hazard; writing only “be careful” does not describe a safe technique.
Similar-looking instruments are not interchangeable: a balance measures mass, while a newton meter measures force. A method is skilful only when it says how the apparatus is used, not merely what it is called; a safety precaution is valid only when it reduces a stated risk in that method.