Speed & Stopping Distances · Topic 1 of 6 · ~1 min read

The Physics of Stopping

Stopping is not one event but two. First your vehicle travels while you perceive, decide, and move your foot — at full speed, with nothing slowing you at all. Only then does braking begin, and physics take over from physiology. Total stopping distance = reaction distance + braking distance. The reason this split matters — and the reason exams test it — is that the two stages scale differently with speed. A normal reaction runs 0.5 to 2 seconds; mid-life drivers (roughly 45–54) actually post the best reaction times in traffic, experience compensating for youth. What follows builds each stage, then puts them back together.

1. 1. Reaction DistanceCalculate reaction distance and identify what stretches and shrinks it.
2. 2. Braking DistanceExplain why braking distance grows with the square of speed, and calculate it.
3. 3. The Full Calculation, WorkedCombine reaction and braking distance into a total stopping distance for any speed.
4. 4. Sorting Factors Into StagesSort any stopping factor into the reaction stage or the braking stage.