# Sophie Duncan lays down some rules for testing response times

This "quick reactions" experiment tests students' responses and introduces the concept of a fair test, while at the same time having some fun.

The experiment involves dropping a ruler and measuring the time it takes to catch it. Pupils need to convert distance dropped into time taken, using the simple formula given below. Primary children can use the conversion table instead.

Pupils work in pairs with the tester holding the ruler at the end with the highest numbers. The test subject places their hand around the bottom of the ruler, making sure they are not touching it. The tester drops the ruler and the subject tries to catch it as quickly as possible. This should be repeated several times to determine the average speed taken to catch the ruler.

The subject should have no warning that the ruler is about to be dropped.

Therefore the tester should drop the ruler within 10 seconds of starting the test, but sometimes doing it immediately and sometimes waiting longer.

Compare different people's response times. Who is the fastest? Make a graph showing all the results. What was the average time? Does age make a difference? Compare with other classes' times. Does it make a difference if it is the morning or afternoon, and if you have just eaten or not? Repeat the experiment and see if you can improve your response time.

To work out the response time, you need a formula that gives the distance travelled by an object in a given time. This is determined by g, the acceleration due to gravity, which is 980cm per second squared. Distance, d (in cm), is equal to a half times g, times the response time, t (in seconds), squared. d = 1Z2 x g x t2. Therefore t = C2dZg The following table gives the time for each distance

Sophie Duncan is project manager for science at the BBC

www.bbc.co.ukscience

It only takes a moment and you'll get access to more news, plus courses, jobs and teaching resources tailored to you

## Latest stories

Kate Parker
26 May 2018
• ### Why we need better training behind bars

Stephen Exley
26 May 2018
• ### 'In a world of opportunity, why limit young people’s scope?'

Julia Belgutay
26 May 2018
• ### Joe Wicks profile: ‘Kids are not doing exercise'

Eleanor Busby
26 May 2018

Ann Mroz
26 May 2018
• ### Why misbehaviour isn’t just a free choice

Joshua Morris
26 May 2018
• ### £4m for educational psychologists in Scotland

Henry Hepburn
26 May 2018

Tes Reporter
25 May 2018
• ### £100 uniform subsidy for poor Scottish pupils

Henry Hepburn
25 May 2018

David Weston
25 May 2018