Human Reaction Time

Key Stage 4

Meaning

Reaction time is the time it takes between stimulus and response.

About Reaction Time

The reaction time is how long it takes to react to a change in the environment.

Reaction time affects how far a car will travel before the driver applies breaks for an emergency stop, eg if someone jumps out into the road the driver has to see them, think about it and then apply the breaks. This takes time so the car keeps moving at the same velocity until the breaks are applied.

The reaction time of a human is what causes a thinking distance when stopping a car.

The reaction time of a human can be measured using a variety of experiments where a random event happens and the subject has to respond as quickly as possible. Test your reaction time here

Typical reaction time for a human is around 0.2 seconds.

Method for Testing Reaction Time

The subject places the forearm on a table with the hand hanging over the edge.
A second person holds a metre ruler from the very top and allow it to hang from their fingers with the 0cm mark level with the top of the subject's hand.
The subject holds their index finger and thumb apart allowing the ruler to fall between them.
The second person gives no warning before dropping the ruler.
The subject catches the ruler as quickly as possible between the thumb and index finger.
Record the length of ruler that has passed through the subject's hand in metres.
Convert the distance into reaction time with the following formula:

\[t={{\sqrt{0.2 \times d}}}\]

Where t is the time and d is the distance the ruler has travelled.

References