TL;DR Paper 5 Planning questions are worth 6 - 8 marks and follow a predictable structure: identify variables, state a hypothesis, choose apparatus, write a step-by-step method, and explain how to make results reliable. This guide breaks down each part with worked examples from common Physics setups.
A typical Paper 5 Planning question gives you a context - a physical setup - and asks you to design an experiment to investigate a relationship. You are expected to:
State the independent variable (what you change)
State the dependent variable (what you measure)
List controlled variables (what you keep constant)
Write a hypothesis (a testable prediction with reasoning)
Mass of bob, amplitude of swing, same protractor for angle
Common mistake: Writing "keep everything else the same" instead of naming specific controlled variables. Examiners award marks for named factors.
Writing a hypothesis
A strong hypothesis has three parts:
A prediction of the relationship
A reason based on physics
Clear reference to the variables
Weak: "The longer the string, the longer the time."
Strong: "As the length of the pendulum string increases, the period of one oscillation increases, because a longer pendulum has a greater arc to travel through for the same amplitude."
3 | Common Planning setups in Combined Science Physics
Setup A: Resistance and wire length
Context: Investigate how the length of a constantan wire affects its resistance.
Component
Detail
Independent variable
Length of wire (measure with metre rule, in cm)
Dependent variable
Resistance (calculated from V/I using voltmeter and ammeter)
Controlled variables
Same wire material and diameter, same power supply voltage, same temperature (allow cooling between readings)
Key apparatus
Constantan wire (SWG 26 or 28), metre rule, crocodile clips, ammeter (0 - 1 A), voltmeter (0 - 5 V), d.c. power supply
Method outline:
Set up the circuit with ammeter in series and voltmeter in parallel across the wire.
Use crocodile clips to connect the wire at 20.0 cm length.
Switch on and record ammeter reading (I) and voltmeter reading (V).
Switch off promptly to avoid heating.
Calculate resistance R = V ÷ I.
Repeat for lengths 30.0, 40.0, 50.0, 60.0, 70.0, 80.0 cm.
For each length, repeat the reading 3 times and calculate the mean resistance.
Plot a graph of R (y-axis) against length (x-axis).
Setup B: Cooling rate and insulation
Context: Investigate how insulation material affects the rate of cooling of hot water.
Component
Detail
Independent variable
Type of insulation (cotton, newspaper, bubble wrap, no insulation)
Dependent variable
Temperature of water at fixed time intervals
Controlled variables
Same volume of water (e.g. 200 ml), same starting temperature, same beaker size, same thermometer
Method outline:
Wrap a 250 ml beaker with the first insulation material (one layer, same thickness).
Pour 200 ml of water at 80 °C into the beaker.
Record temperature every 60 seconds for 10 minutes using a thermometer (read to 0.5 °C).
Repeat with each insulation type and with no insulation (control).
Plot temperature-time curves for all conditions on the same axes.
Compare the rate of cooling by finding the gradient at a common temperature.
Setup C: Light intensity and distance
Context: Investigate how the distance from a lamp affects the light intensity reaching a surface.
Component
Detail
Independent variable
Distance from lamp to LDR (in cm)
Dependent variable
Resistance of LDR (measured with ohmmeter or voltmeter - ammeter)
Controlled variables
Same lamp at same brightness (constant voltage), same LDR, dark room, same angle
4 | Writing the method: mark-scoring habits
What earns marks
Numbered steps (not bullet points)
Specific quantities ("pour 200 ml of water" not "pour some water")
Named instruments ("measure with a metre rule to the nearest mm")
Safety notes where relevant ("allow wire to cool for 30 seconds between readings")
Repeat statement ("repeat each reading 3 times and calculate the mean")
What loses marks
Vague language: "measure the temperature" without saying how often or with what
Missing apparatus specification: "use a ruler" instead of "use a metre rule (0 - 100 cm, ± 0.1 cm)"
No repeat or averaging statement
Not stating what to plot on which axis
5 | Reliability and accuracy phrases
Use these phrases in your Planning answer:
Concept
Phrase to use
Repeats
"Repeat the measurement 3 times for each value of [IV] and calculate the mean to reduce random error."
Fair test
"Keep [controlled variable] constant throughout by [specific action]."
Accuracy
"Use a [specific instrument] to measure [quantity] to the nearest [resolution]."
Anomaly handling
"Identify and discard anomalous results before calculating the mean."
Zero error
"Check for zero error on [instrument] before starting."
6 | Practice Planning question (worked)
Question: Design an experiment to investigate how the mass attached to a spring affects the extension of the spring.
Model answer:
Hypothesis: As the mass attached to the spring increases, the extension increases proportionally, because a greater gravitational force stretches the spring further (Hooke's law region).
