LuduminaFM-13 · FM-U4 · Planned
Reaction time and safe stopping
Learning objectives
Separate thinking/braking distance; explain road, tyres, brakes and human factors; H: estimate deceleration forces.
8463 §§4.5.6.3.1–4.5.6.3.4 / 8464 §§6.5.4.3.1–6.5.4.3.4
DfE single-science pp.35–37 / Combined pp.30–32. Evidence checked 30 September–1 October 2026. Skills: WS1.5,2.2,3.4,3.7; MS2b,2c,2f,2h,3c.
Explanation
Thinking distance is travel before braking starts; braking distance is travel while the brakes reduce kinetic energy. Human factors change reaction time; road and vehicle condition change braking. A fixed-braking-force model makes braking distance grow with speed squared.
Concepts, equations and units: Stopping distance=thinking+braking; thinking distance≈v t_reaction; typical reaction times 0.2–0.9 s; KE and work models; H force estimate.
Prediction, demonstration and game exercise
Predict, observe, explain
Compare identical speeds with different reaction times and surfaces; expose simulated human delay rather than measuring network lag.
Planned learner game exercise
Test a virtual road safety plan with distraction, tiredness, weather and tyre-condition cards; propose a ruler-drop method.
Independent practice
Summarise reaction-time repeats with mean/mode/median and histogram; plan representative participant sampling; calculate stopping distances. P: interpret speed–stopping-distance graphs for multiple vehicle types and estimate emergency-stop distances for a typical speed range. H: estimate forces.
Original practice example · Shared
At 15 m/s with reaction time 0.40 s and braking distance 18 m, find total stopping distance.
Show working and model answer
Working / reasoning
Thinking = vt = 15 × 0.40 = 6 m; stopping = 6 + 18.
Answer
24 m.
Exit check and success criteria
Two correct distances plus two causal factors and one data limitation; H estimate states assumptions.
During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.
Misconceptions, practical links and mastery
Check these misconceptions
Wet roads slow reactions; doubling speed only doubles braking distance under a fixed braking-force model.
Practical preparation
Optional teacher-supervised reaction-time study; not an RP.
Virtual preparation and revision only. Required hands-on activities and school records remain separate.
Proposed mastery
0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.