# Stopping Distance Formula

If a driver puts on the brakes of a car, the car will not come to a stop immediately. The stopping distance is the distance the car travels before it comes to a rest. It depends on the speed of the car and the coefficient of friction (*μ*) between the wheels and the road. This stopping distance formula does not include the effect of anti-lock brakes or brake pumping. The SI unit for stopping distance is meters.

*d* = stopping distance (*m*)

*v* = velocity of the car (*m/s*)

*μ* = coefficient of friction (unitless)

*g* = acceleration due to gravity (9.80 m/s^{2})

Stopping Distance Formula Questions:

1) A driver in a car on a residential street is traveling at 50.0 *km/h*. She puts on the brakes when she sees a stop sign. The coefficient of friction between the tires and the road is *μ* = 0.60. What is the stopping distance of the car?

Answer: The speed of the car must be converted to meters per second:

v = 13.89 *m/s*

The stopping distance can be found using the formula:

d = 16.40 *m*

The stopping distance of the car is 16.40 m.

2) A driver in a car on an icy highway is traveling at 100.0 *km/h*. He puts on the brakes and begins to slide. The coefficient of friction between the tires and the ice on the road is *μ* = 0.15. What is the stopping distance of the car?

Answer: The speed of the car must be converted to meters per second:

*v = 27.78 m/s*

The stopping distance can be found using the formula:

d = 262.4 *m*

The stopping distance of the car on an icy highway is 262.4 *m*.

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