AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    Reaction times vary from person to person. Typical values range from 0.2 s…

    Full specification wording

    Reaction time: Reaction times vary from person to person. Typical values range from 0.2 s to 0.9 s.

    Reaction times are personal: typical values run from about 0.2 s for an alert, practised person to about 0.9 s.

    Checked against the AQA 8463 specification (opens in a new tab) on .

    • Point 1 of 2
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Reaction times are personal: typical values run from about 0.2 s for an alert, practised person to about 0.9 s. They can be measured simply by the ruler drop test, where one student releases a metre rule between another's fingers and the catch distance is converted to a time, or more precisely by a computer test that records the delay between a signal and a key press. Both need several trials and a mean, because reaction time varies from attempt to attempt. The effect on the road is large: at 30 m/s a 0.2 s reaction covers 6 m, while 0.9 s covers 27 m, over four car lengths more before the brakes have done anything at all. Because the values vary so much between people, a class set of results should be reported as a mean together with the range.

    What earns the marks

    • Quoting a typical reaction time inside the range 0.2 s to 0.9 s.
    • Using thinking distance = speed × reaction time.
    • A correct substitution such as 30 × 0.7.
    • The answer in metres.

    Common mistakes and how to put them right

    • Quoting a reaction time in milliseconds and then substituting the number without converting to seconds.

    • Giving a reaction time of several seconds, far outside the typical range.

    • Taking a single measurement rather than repeating and finding a mean.

    • Assuming every driver has the same reaction time, so one measured value applies to all.

    Exam tips

    • Learn the range 0.2 s to 0.9 s as a recall fact; questions often ask for a typical value with no data given.
    • State the reaction time you are using before the substitution so the examiner can follow it.
    • If asked to comment on a measured value, compare it with the typical range rather than calling it right or wrong.

    Try the lesson

    The start of the Reaction time: Reaction times vary from person to person. Typical values range from 0.2 s to 0.9 s. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of these is a typical reaction time for a person?

    Listen

    Reaction times are personal: typical values run from about 0.2 s for an alert, practised person to about 0.9 s. They can be measured simply by the ruler drop test, where one student releases a metre rule between another's fingers and the catch distance is converted to a time, or more precisely by a computer test that records the delay between a signal and a key press. Both need several trials and a mean, because reaction time varies from attempt to attempt. The effect on the road is large: at 30 m/s a 0.2 s reaction covers 6 m, while 0.9 s covers 27 m, over four car lengths more before the brakes have done anything at all. Because the values vary so much between people, a class set of results should be reported as a mean together with the range. A strong answer earns marks for these points. quoting a typical reaction time inside the range 0.2 s to 0.9 s. using thinking distance = speed × reaction time. a correct substitution such as 30 × 0.7. the answer in metres. Exam tip: Learn the range 0.2 s to 0.9 s as a recall fact; questions often ask for a typical value with no data given.

    See it

    A top-down flowchart. The first box says reaction time varies from person to person and points to a box saying typical values range from 0.2 s to 0.9 s. That box branches into two: one box for 0.2 s, an alert, practised person, and one box for 0.9 s. The 0.2 s box leads to a box saying that at 30 m/s, 0.2 s covers 6 m. The 0.9 s box leads to a box saying that at 30 m/s, 0.9 s covers 27 m. Both of these final boxes point to a single box saying this is over four car lengths more before the brakes have done anything.
    It shows the typical reaction time range of 0.2 s to 0.9 s and how the thinking distance at 30 m/s grows from 6 m to 27 m across that range.

    Key words

    Say what each word means before you turn the card.

    typical reaction times

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    variation between people

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    ruler drop test

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    repeats and means

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    See every definition
    typical reaction times
    Values that range from 0.2 s to 0.9 s, varying from person to person.
    variation between people
    Because values vary so much between people, a class set of results should be reported as a mean together with the range.
    ruler drop test
    One student releases a metre rule between another's fingers and the catch distance is converted to a time.
    repeats and means
    Several trials and a mean are needed because reaction time varies from attempt to attempt.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The first box says reaction time varies from person to person and points to a box saying typical values range from 0.2 s to 0.9 s. That box branches into two: one box for 0.2 s, an alert, practised person, and one box for 0.9 s. The 0.2 s box leads to a box saying that at 30 m/s, 0.2 s covers 6 m. The 0.9 s box leads to a box saying that at 30 m/s, 0.9 s covers 27 m. Both of these final boxes point to a single box saying this is over four car lengths more before the brakes have done anything.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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