Final answer:
The stopping distance required for a vehicle increases with the square of its speed; thus, at 40 mph the stopping distance is four times greater than at 20 mph, making option A the correct answer.
Step-by-step explanation:
When managing speed and during braking, it's important to know that the stopping distance of a vehicle increases with the square of its speed. This means that a car traveling at 40 mph does not simply need twice the distance to stop compared to one traveling at 20 mph; it requires significantly more. Specifically, the stopping distance required at 40 mph is four times greater than that at 20 mph due to the physics of deceleration.
The relationship between speed and stopping distance is not linear but quadratic, which is why higher speeds result in disproportionately greater stopping distances. This implies that drivers must be aware of their speed in relation to their ability to stop safely, especially in conditions where reaction times and surface conditions, such as wet roads, can further extend the distance required to come to a complete halt.
Therefore, the correct answer to the question, 'Which of the following is true about speed management and braking?' is A. The stopping distance required for vehicles at 40 mph is four times greater than that required at 20 mph.