Measuring Reaction Time (Edexcel GCSE Physics): Revision Note

Measuring Reaction Time

• The reaction time is defined as:

  A measure of how much time passes between seeing something and reacting to it

• The human reaction time for someone who is alert - i.e. someone waiting to react to something happening, like an athlete waiting for the start of a race - is usually in the range of 0.2 - 0.9 seconds

• A simple method for measuring human reaction time is illustrated below:

Dropping a ruler provides a simple and fun way of measuring someone’s reaction time

• Person A holds a 30 cm ruler vertically, such that the bottom end of the ruler hovers over the top of the hand of Person B

• Person A should release the ruler unexpectedly

• As soon as Person B sees the ruler move, they should close their hand, catching it

• The ruler is marked at the point at which it was caught by Person B - i.e. in line with the top of their hand

• This gives a measurement of the distance the ruler fell

  • The greater the distance, the longer the reaction time