Core Practical: Investigating Reaction Time

This lesson covers the core practical on investigating reaction time using the ruler drop test, as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the method, identify variables, calculate reaction time, evaluate results and suggest improvements to accuracy.

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Introduction

Reaction time is the time it takes for a person to respond to a stimulus. It is a measure of how quickly the nervous system can detect a stimulus, process it and produce a response.

Typical human reaction times:

Response Type	Typical Reaction Time
Visual stimulus (e.g. catching a ruler)	200–300 ms (0.2–0.3 s)
Auditory stimulus (e.g. responding to a sound)	150–250 ms
Touch stimulus	150–200 ms

This practical uses the ruler drop test to measure reaction time. It tests the reaction time of the nervous system: Stimulus (ruler drops) → Receptor (eyes detect movement) → Sensory neurone → CNS → Motor neurone → Effector (hand muscles close) → Response (ruler caught).