North Carolina RADAR State Practice Exam

How long does the stopping distance become at 40 MPH as compared to 20 MPH?

1. It doubles

2. It is more than triple

3. It quadruples

4. It remains the same

The correct answer is: It quadruples

When considering stopping distances in relation to speed, it's important to understand the physics involved. The stopping distance is comprised of two main components: the reaction distance (the distance traveled while a driver reacts to a hazard) and the braking distance (the distance traveled while the vehicle is coming to a stop). As speed increases, both the reaction distance and braking distance increase, but the braking distance increases with the square of the speed. This means that if you double your speed, the braking distance quadruples. For instance, at 20 MPH, the stopping distance is a certain number of feet. When the speed increases to 40 MPH, the braking distance will be four times that of the 20 MPH distance due to this square relationship. Therefore, the total stopping distance at 40 MPH is indeed quadrupled compared to the stopping distance at 20 MPH. Thus, it is crucial for drivers to be aware that as their speed increases, they need to allow significantly more distance to come to a complete stop, underlining the importance of maintaining appropriate speeds and following distance to ensure safety on the road.