Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Explain methods of measuring human reaction times and recall typical results
Full specification wording
Topic 2 – Motion and forces: 2.27 Explain methods of measuring human reaction times and recall typical results
Human reaction time is measured by presenting a signal and recording how long the person takes to respond.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 26 of 32
Study notes
From the checked teaching notes for this specification point.
The idea
Human reaction time is measured by presenting a signal and recording how long the person takes to respond. The common ruler-drop test uses a partner who holds a ruler vertically while the learner places a thumb and finger ready to catch it; the partner releases it without warning and the learner catches it. The distance the ruler falls is read from the scale and converted to a time using a conversion table or the equation for free fall, giving a typical value of about 0.2 s. A computer-based test flashes a stimulus and records the key-press time electronically, which is more precise. Repeat trials and average the results to reduce random error.
What earns the marks
- Identifies the ruler-drop test as a method in which a partner releases a ruler and the learner catches it.
- States that the distance the ruler falls is converted into a reaction time using a table or free-fall equation.
- Recalls a typical human reaction time of about 0.2 s.
- Describes an electronic or computer method that times a response to a signal.
- Explains that repeated trials are averaged to reduce random error.
Common mistakes and how to put them right
Confuses reaction time with the distance the ruler falls.
Put it right: Convert the distance to a time before quoting a result.
Quotes a typical reaction time of several seconds.
Put it right: Use a value of about 0.2 s.
Treats a single trial as reliable.
Put it right: Repeat and average the readings.
Assumes the catcher should watch the partner's hand.
Put it right: The release must be unpredictable so the response is genuine.
Exam tips
- Learn one practical method in detail, including how the fall distance becomes a time.
- Remember the typical value of about 0.2 s and use it when a question asks for a sensible estimate.
- Link repeats and averaging to reducing random error whenever a method question appears.
Try the lesson
The start of the Topic 2 – Motion and forces: 2.27 Explain methods of measuring human reaction times and recall typical results lesson, made from checked teaching notes for this specification point.
Have a go first
In the ruler-drop test for reaction time, what does the distance the ruler falls before it is caught measure?
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