How to Calculate an Auto's Braking Distance

Doubling your speed increases your stopping distance four times.

Your vehicle stops once the friction from the surface it is traveling on has performed work equal to the vehicle's kinetic energy. The work is the product of the vehicle's mass, the distance it travels, its coefficient of friction with the road and its gravitational acceleration, all of which increase friction. The kinetic energy is half the product of the vehicle's mass and the square of its velocity. You can calculate any of these components, including the vehicle's stopping distance, through the equation for when friction equals kinetic energy, which is: μmgd = 0.5mv^2.

Instructions

1. Square the automobile's velocity (v) . If it travel's, for instance, at 15 meters per second: 15^2 = 225.

2. Multiply the coefficient of friction (μ) by 2. This figure is 0.8 with good tires and normal conditions, though ice or oil can reduce it. With a coefficient of 0.08: 0.08 x 2 = 0.16.

3. Multiply the result by the acceleration due to gravity (g), which is a constant that equals 9.81 meters per second squared: 0.16 x 9.81 = 1.59.

4. Divide the vehicle's squared velocity by the answer from Step 3: 225 / 1.59 = 142. The vehicle's stopping distance (d) is 142 meters.

References

• Georgia State University: Stopping Distance Calculation
• University of Alaska: Static and Kinetic Friction

Resources

• University of Oklahoma: Night Driving
• Manitoba Department of Education: Braking