Tools and Inquiry — IB Physics skills
I.1.2 Designing in Physics — IB Physics HL Revision Notes & Topical Questions
5 min read 9 parts Lesson 16 of 22 1 quiz
Lesson summary
I.1.2 Designing in Physics — IB PHYSICS SL notes: Design a valid, safe and reproducible methodology with justified variables, ranges and repeats.Turn the research question into a practical, step-by-step plan.Collect sufficient, high-quality data to answer the question.Explain cle…
- Independent variable (IV)
- Dependent variable (DV)
- Controlled variables (CVs)
- Give units and how each variable is measured
- Range of the independent variable
- Timing many oscillations and dividing
Part 1 of 7Aim of the design
Aim of the design
Turn the research question into a practical, step-by-step plan.
Collect sufficient, high-quality data to answer the question.
Explain clearly the variables, measurements and all safety aspects.
Part 2 of 7Identifying and justifying variables
1Independent variable (IV)
Independent variable (IV) the single variable deliberately changed.
2Dependent variable (DV)
Dependent variable (DV) the variable measured to see the effect of the change.
3Controlled variables (CVs)
Controlled variables (CVs) all other factors that could affect the outcome.
- Explain how each will be kept constant — to make a fair test.
4Give units and how each variable is measured
- Give units and how each variable is measured e.g. length from the suspension point to the centre of the bob in metres.
Part 3 of 7Range and quantity of measurements
Range and quantity of measurements
Range of the independent variable
- Range of the independent variable a suitable range with at least five different values to show a clear trend.
- Justify the choice, e.g. lengths too short give a period too rapid to time, lengths too long are impractical.
Quantity
- Quantity repeat for each value of the independent variable, with at least three trials.
- Repeats allow a mean — which reduces the effect of random error.
- Repeats help identify and discard anomalous results.
Timing many oscillations and dividing
- Timing many oscillations and dividing reduces the effect of reaction time.
Part 4 of 7Writing the methodology
Writing the methodology
A logical sequence of instructions that another physicist could follow exactly.
Precise apparatus details
- "1.0 m ruler with 1 mm divisions", not "a ruler".
Structure the report.
- Materials and apparatus, with a labelled diagram of the set-up.
- Safety, ethical and environmental points, with a brief risk assessment and specific precautions.
- Numbered step-by-step procedure.
Creativity can show in solving a measurement problem
- Creativity can show in solving a measurement problem video analysis of a falling object is more reliable than a stopwatch.
Be specific about safety
- Be specific about safety a crash mat under a pendulum bob and a heavy base on the retort stand, not "be careful".
Part 5 of 7Other approaches
Databases
- Databases use established data for a property such as star luminosity, then process it to find a trend.
- (e.g. NASA or CERN)
Simulations
- Simulations collect data from a simulation (e.g. PhET) for a process too difficult or dangerous for school,
- such as particle collisions or gravitational fields.
Justify the choice of source and state the parameters and settings used.
Part 6 of 7Pilot study and justification
1Pilot study
Pilot study a small-scale trial run of the experiment.
- It checks the method works, e.g. that a meter is connected correctly and the power supply gives a suitable range.
2Justify choices
- Justify choices why this apparatus, this range and these controls — thinking like a physicist.
3Be specific about instruments
- Be specific about instruments name the instrument and its uncertainty in the method.
4
Examples of specific controls.
- Wire resistancesame wire, low current to avoid heating, micrometer at several points for diameter.
- Specific heat capacity by mixturesinsulated polystyrene cup with lid, quick transfer, maximum temperature recorded.
Part 7 of 7More from the specification
More from the specification
Scientific Hypothesis Formulation
- A rigorous scientific investigation begins with a testable hypothesis defining the expected mathematical relationship between independent and dependent physical quantities.
Experimental Design and Control
- In an investigation measuring the thermal capacity of a metal block heated in boiling water, the experimenter must control potential heat loss and provide methodological justification to ensure reliable and repeatable data.
Validation of Energy Conservation
- When designing experiments involving thermal or mechanical energy transformations, procedures must ensure energy losses to surroundings are minimized to validate theoretical conservation equations.
- (such as simple pendulum motion or calorimeter tests)
Scientific Hypothesis Formulation
- A rigorous scientific investigation begins with a testable hypothesis defining the expected mathematical relationship between independent and dependent physical quantities.
Experimental Design and Control
- In an investigation measuring the thermal capacity of a metal block heated in boiling water, the experimenter must control potential heat loss and provide methodological justification to ensure reliable and repeatable data.
Validation of Energy Conservation
- When designing experiments involving thermal or mechanical energy transformations, procedures must ensure energy losses to surroundings are minimized to validate theoretical conservation equations.
- (such as simple pendulum motion or calorimeter tests)
Hypothesis
- Testable prediction with a scientific justification.
Simple pendulum
- A small bob on a light string of length L
Systematic error
- An error that shifts all readings the same way, such as a balance not zeroed.
Directly proportional
- Two quantities increase together in a constant ratio, giving a straight line through the origin.
Small-angle approximation
- Sin θ ≈ tan θ ≈ θ for small θ in radians.
Background radiation
- Radiation that is always present in the environment.
Key terms
| Term | Meaning |
|---|---|
| Independent variable | The variable deliberately changed. |
| Dependent variable | The variable measured as the outcome. |
| Controlled variable | A factor kept constant to give a fair test. |
| Pilot study | Small-scale trial to test that a method works. |
| Methodology | Step-by-step procedure that another person can replicate. |
| Anomalous result | Result that does not fit the pattern of the others. |
Avoid these mistakes
1
Writing a vague method that cannot be replicated.
2
Listing variables without explaining how they are measured or controlled.
3
Using fewer than five values of the independent variable.
4
Not repeating measurements — no mean and no way to identify anomalies.
5
Treating safety as an afterthought with general comments like "be careful".
Marked practiceQuizzes for this lesson
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