Whether you're responding to a starting pistol or hitting a ball served by your opponent, reaction times are enormously important in sport. This activity includes both an interactive computer test of reaction times and suggestions for a hands-on experiment, and encourages younger secondary maths students (Key Stage 3) to make and test hypotheses and to collect and analyse data.

Detailed teachers' notes for this activity are available on our NRICH website.

# Reaction Timer

##### Stage: 3 Challenge Level:

In this problem, you will meet two different ways to test your reactions.

This reaction timer will enable you to collect data on the time it takes you to respond to an image on your computer.

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Note: You can copy/paste the results table into a spreadsheet

Here is a second experiment you can use to test your reactions.
Ask a friend to hold a ruler by the end, above your hand. Open your hand below the ruler and be ready to catch it. Your friend will drop the ruler without saying when they're going to let go. Catch the ruler as fast as you can after it's been dropped.
The pictures below show this experiment being carried out:

Record the level (in centimetres) at which you caught the ruler, and repeat the experiment several times. If you have quick reactions, the ruler will not have travelled far when you catch it.

Taking only one measurement in either of these experiments will not give you a reliable, accurate measure of speeds of reaction that could be used to rank a group of people.

Decide how many measurements you will take, and what you will do with them to provide an accurate measure of reaction speeds. Make sure you can justify your decisions.

#### Here are some questions you might like to consider:

• I think I respond more quickly with my right hand than with my left - are you the same?
• Do your reactions vary depending on the time of day or the sort of thing you are being asked to react to?
• Do your reactions improve with training/practice?
• Do boys react more quickly than girls?
• Do young people react more quickly than older people?
• What else do you think affects people's reaction times?
• Are both experiments testing the same ability? If you perform both experiments with a group of people and rank them in order, will the rankings be the same for both experiments?
• Can you think of other experiments you could do to test your reactions?
Test any hypotheses you come up with.

You may also wish to explore how accurately you can estimate time.

Further information

If you're finding hard to get started, try looking at this hint.

Detailed teachers' notes for this activity are available on our NRICH website.