Learn9702Paper 5 · Planning, Analysis and EvaluationPlanning, analysis and evaluationPlanning an investigation

Planning, analysis and evaluation · Subtopic 1 of 2

Planning an Investigation

Paper 5's planning question gives you a suggested relationship, such as $T=km^n$ , and asks for a full plan. Identify the independent variable (what you change), the dependent variable (what you measure) and the control variables (what you keep constant). Describe exactly how each is measured, with named instruments and a labelled diagram. Say what graph you'll plot to get a straight line, how to find constants from it, and include specific safety precautions and extra detail for reliability.

Cambridge 9702 Paper 5Edexcel YPH11 WPH16AQA 7408 Paper 3A≈ 40 minRevision 5 · updated 2026-10-27

Section 1 of 14

Learning objectives

Identify independent, dependent and control variables.
Describe methods to vary and measure variables, with apparatus.
Choose a graph that tests the relationship and gives constants.
Include specific safety and reliability details.

Pause and think

You're asked to investigate how the current in a solenoid affects the magnetic field inside it. What would you change, what would you measure, and what must stay the same?

Section 2 of 14

Core idea

Start hereDesigning an experiment on paper

In the planning question you never touch apparatus. You must convince the examiner that someone could follow your plan and get a clear answer, including how to turn the data into a straight-line graph.

The big idea

Variables; method and apparatus; analysis (linearise to $y=mx+c$ ); safety and extra detail.

1. Structure

Example: how does the period of a mass on a spring depend on the mass?

Analysis:

T=2\pi\sqrt{m/k}

, so plot

T^2

against

m

; a straight line through the origin with gradient

\dfrac{4\pi^2}{k}

confirms it.

A complete plan

Drawing diagram…

Every box earns marks.

Worked exampleTesting $T=2\pi\sqrt{\frac mk}$

Plan an experiment.

Goal: Outline plan.
Strategy: Follow the structure.

Variables: change $m$ ; measure $T$ ; same spring.
Method: time 20 oscillations; fiducial marker at equilibrium.
$T^2=\frac{4\pi^2}k\,m$
Plot $T^2$ against $m$ : straight line through the origin, gradient $\frac{4\pi^2}k$ .
Safety: secure clamp stand; goggles in case the spring snaps.

AnswerRelationship confirmed if the graph is straight through the origin.

✓ Check

k=4\pi^2/\text{gradient}

can be compared with a static measurement ✓.

Finding an unknown power

n

$y=ax^n$
Suspected relationship.
$\lg y=n\lg x+\lg a$
Logs: plot $\lg y$ against $\lg x$ ; gradient $n$ .

Common misconceptionVague methods "Measure the length" earns nothing; "measure

l

with a metre rule from the pivot to the centre of the bob" does.

Summary

Variables, method, analysis, safety.

Control variable: Kept constant.

HistoryFizeau's speed of light. In

1849

Hippolyte Fizeau planned an experiment to measure the speed of light with a spinning cogwheel and a mirror

8

km away. Light passed through a gap, reflected and returned; at the right speed, the next tooth blocked it. Careful planning turned a seemingly impossible measurement into a result within

5\%

of today's value.

Fun factPlanning at CERN. The Large Hadron Collider took around

25

years from planning to first collisions. Experiments are planned years ahead, with simulations of exactly what data will be collected and how it will be analysed, before a single proton is fired.

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