Calculadora de Distância de Parada
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
d_total = v·t_reação + v² / (2·μ·g)
About this calculator
The Stopping Distance Calculator determines the distance needed for an object to come to a complete stop under constant friction. It uses the formula d = v²/(2μg), where d is the stopping distance, v is the initial velocity, μ is the coefficient of friction between surfaces, and g is the acceleration due to gravity (approximately 9.8 m/s²). This tool is useful for drivers, engineers, and anyone needing to estimate braking distance under different road conditions.
The calculation is based on energy conservation: initial kinetic energy (½mv²) is dissipated by the work done by friction (μmgd). Equating these expressions yields the formula. The user inputs speed in km/h or m/s, the friction coefficient (a table is provided), and optionally local gravity. The calculator converts speed to m/s, applies the formula, and displays the distance in meters. It also shows stopping time and deceleration.
When to use: traffic safety planning, runway design, accident analysis, sports (e.g., bicycle or car braking), physics education. Example: a car at 72 km/h (20 m/s) on dry asphalt (μ=0.7) needs about 29 meters to stop. On wet pavement (μ=0.4), the distance increases to 51 meters. The calculator helps raise awareness about the importance of speed and friction.
Cautions: the formula assumes constant friction and ignores air resistance, road grade, driver reaction time, and dynamic brake conditions. In real scenarios, total stopping distance includes reaction time (distance traveled before braking). For better accuracy, use realistic friction coefficients (consult technical tables) and note that friction may vary with speed and tire wear. This calculator is an educational and estimation tool, not a substitute for practical testing.
Frequently asked questions
What does the friction coefficient μ mean?
The friction coefficient μ is a dimensionless number representing the roughness between two surfaces. Typical values: dry asphalt μ≈0.7, wet asphalt μ≈0.4, ice μ≈0.1. Higher μ means more friction and shorter stopping distance.
Does the calculator consider driver reaction time?
No. The formula only calculates braking distance after brakes are applied. Total stopping distance includes reaction distance (velocity × reaction time, about 1.5 seconds). Add d_reac = v * t_reac to get total distance.
Can I use the calculator for any vehicle?
Yes, as long as deceleration is mainly due to tire-road friction. For trains or planes, consider other factors like aerodynamic brakes. The formula is a good approximation for cars, bicycles, and sliding objects.
What speed unit should I use?
The calculator accepts km/h or m/s. Internally, it converts to m/s. If using km/h, divide by 3.6 to get m/s. Example: 72 km/h = 20 m/s. Stopping distance will be in meters.
Is the result accurate for real situations?
It is an estimate. Accuracy depends on correct friction coefficient and ideal conditions (flat road, no wind, perfect brakes). In emergencies, actual distance may be longer due to unmodeled factors.