Final answer:
The distance a car travels during the driver's reaction time before brakes are applied is called the reaction distance, which adds to the overall stopping distance.
Step-by-step explanation:
The distance a car travels in the time it takes the driver to react to a hazard and step on the brakes is called the reaction distance.
When a driver senses a hazard and decides to apply the brakes, there is always a brief delay before the physical action takes place. This delay is the reaction time, which in various examples and calculations is often assumed to be around 0.500 seconds.
During this reaction time, the car continues to travel at its initial speed. For example, if a car is traveling at 30.0 m/s and the driver's reaction time is 0.500 seconds, the reaction distance will be the product of the speed and the reaction time, which equals 15.0 meters. This distance must be added to the braking distance, the distance the car travels after the brakes are applied until it comes to a complete stop, to calculate the total stopping distance.