AQA Biology 4.5.2.1 · Combined 4.5.2
Reaction time
Drop a ruler, catch it, and turn the distance into a time. Then test whether one factor changes it.
Combined Science · Higher tier
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Catch!
Someone knocks a phone off the table and you grab for it.
If you had to guess, are you quicker to catch it when you’re wide awake, or when you’re tired?
Required practical 6
The ruler drop.
Reaction time is the time between a stimulus and your response. A partner holds a ruler vertically with 0 cm level with the top of your thumb and finger. Without warning, they drop it; you catch it. Read the distance at the top of your thumb. The longer the distance, the longer the reaction time. Test one factor: distraction, by doing mental arithmetic while you catch.
Pick a condition, then drop the ruler three times.
The conversion table turns a distance into a time. Check its units: here distance is in cm and time in s.
Planning one? Tap each part.
Typical reaction times range from 0.2 s to 0.9 s; for a simple stimulus like this, about 0.2–0.3 s. Alcohol, tiredness and distraction slow reactions; caffeine is a stimulant and speeds up the nervous system. The pathway itself: The nervous system.
Method · mean of repeats
mean = total of the repeats ÷ number of repeats
Written out
Measurements are affected by random error: results vary in unpredictable ways. Repeating and reporting a mean reduces the effect. Put every repeat in the same unit first: ms ÷ 1000 gives s, so 240 ms = 0.24 s. A distance in m or mm must go into cm before you use the table: m × 100; mm ÷ 10, so 120 mm = 12 cm.
Think again · further means faster?
“Further down the ruler means faster reactions.”
Your call
ChoosePupil A catches the ruler at 12 cm. Pupil B catches it at 30 cm. Who reacted faster?
Sort
Which variable?
Distraction investigation. Place each one.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Plan
- Variables, method, repeats, safety and ethics, and how you’ll show the results.
- Calculate
- A mean, with every repeat in the same unit.
- Use the table
- Distance to time, units checked first.
Key fact
A longer catch distance means a longer reaction time. Read times from the conversion table, repeat, and report a mean.
Key note · AQA 4.5.2.1 (Combined 4.5.2) · RP 6 / RP 7
Reaction time
- Reaction time: the time between a stimulus and a response. Typical values 0.2 s to 0.9 s; about 0.2–0.3 s for a simple stimulus.
- Ruler drop: 0 cm at the top of the thumb, drop without warning, read the catch distance. Longer distance, longer time.
- Use the conversion table, units checked. Repeat and report a mean to reduce random error.
- Change one factor, control the rest, act safely and ethically, and show the means as a bar chart.
Photograph this card. Tomorrow, cover it and say each line first.
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Not sure which unit the table wants?
Catch distances and the conversion table are teaching values.