Two students compare reaction times with and without background music. They always test without music first. The mean reaction time is shorter when music is playing. Which change would best help them decide whether the difference is caused by music rather than practice?
Alternate the test order and repeat both conditions.
Keep the test order and repeat only with music.
Alternate the ruler length and repeat both conditions.
Keep the ruler length and use only the fastest results.
126 exam-style questions on Edexcel GCSE Physics 2.5 Stopping and braking distances, covering 2.5.1 Stopping distance and reaction time, 2.5.2 Factors affecting stopping distance, 2.5.3 Dangers of large decelerations, and 2.5.4 Braking distance and initial speed. Each one has a worked solution and a mark scheme showing where the marks go.