Reaction time can be investigated by catching a dropped ruler or using a timed response task. A ruler drop distance can be converted to time using a supplied conversion chart; control the starting position and avoid giving a predictable release cue. Repeat trials, compare means and spreads, and distinguish practice effects from a genuine change in reaction time. This is an investigation, not an AQA required practical. Use clear labels. Explain the result. Relate the result to the physical model.