--- title: "Stopping Distances and Braking Energy" description: "Stopping distance splits into thinking distance, set by reaction time and speed, and braking distance, set by the work the brakes must do to empty the kinetic store. Braking distance grows with the sq" canonical: https://lightmysky.com/learn/science/stopping-distances-and-braking-energy-mt_nRNZS4jHoj source: https://lightmysky.com/learn/science/stopping-distances-and-braking-energy-mt_nRNZS4jHoj.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Stopping Distances and Braking Energy Stopping distance splits into thinking distance, set by reaction time and speed, and braking distance, set by the work the brakes must do to empty the kinetic store. Braking distance grows with the square of the speed. Subject: Science · Area: Forces & Motion · Ages 15 to 16 Page: https://lightmysky.com/learn/science/stopping-distances-and-braking-energy-mt_nRNZS4jHoj ## Ready when they can - Calculates thinking distance from a reaction time and a speed - Uses the kinetic store and the braking force to work out a braking distance - Explains why doubling the speed roughly quadruples the braking distance, and lists what makes each part longer ## Lesson: Why speed squares your stopping Stopping distance splits in two for you. Thinking distance is the ground covered while you notice danger and react, before your foot touches the brake. Braking distance is the ground covered while the brakes drain the kinetic store to zero. **Example.** Thinking distance is speed times reaction time. At 20 m/s with a 0.6 s reaction, you travel 20 times 0.6 = 12 m before braking even starts. Tiredness, distraction, and drink stretch the reaction, and higher speed covers more ground in the same time. Braking distance comes from work: brake force times distance = kinetic store removed. Since the store grows with speed squared, doubling speed from 15 m/s to 30 m/s roughly quadruples the braking distance. Worn brakes, worn tyres, wet roads, and heavy loads all stretch it further. **Tip.** Answer stopping questions in three beats: thinking distance, braking distance, then the total. Say which part each factor touches: phones and drink hit thinking, rain and bald tyres hit braking. **Recap.** Reaction times speed for thinking, speed squared for braking, and the total is both added. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Kinetic and Gravitational Potential Stores](https://lightmysky.com/learn/science/kinetic-and-gravitational-potential-stores-mt_uD3jklaZCw) - [Calculating Work Done and Power](https://lightmysky.com/learn/science/calculating-work-done-and-power-mt_udulQxseg1) ## Opens up - [Specific Heat Capacity as a Material Property](https://lightmysky.com/learn/science/specific-heat-capacity-as-a-material-property-mt_mXC9IKom3P)