Final answer:
Hydroplaning typically occurs on a wet road surface starting at about 35 mph (56 km/h). This is when the tires of a vehicle lose contact with the road due to a layer of water, leading to a loss of control. Understanding the effect of road conditions on stopping distances is critical for safe driving. Therefore, the correct answer is option a. On a wet road surface starting at about 35 mph.
Step-by-step explanation:
Hydroplaning typically occurs on a wet road surface starting at about 35 mph (56 km/h). This phenomenon happens when a layer of water builds up between the tires of a vehicle and the road surface, leading to a loss of traction that prevents the vehicle from responding to control inputs.
It's crucial for drivers to slow down in wet conditions to avoid hydroplaning. To understand this concept better, let's analyze the scenario of stopping distances on different road conditions.
In Example 2.12, the situation involves a car traveling at a speed of 30.0 m/s on different surfaces and having different deceleration rates. On dry concrete, the car can decelerate at a rate of 7.00 m/s², while on wet concrete, it can only decelerate at a rate of 5.00 m/s². These differences significantly affect the distance needed to bring the car to a complete stop.
For instance, if a driver sees a traffic light turn red and has a reaction time of 0.500 s, the stopping distance gets increased by the distance the car travels during that reaction time. In both dry and wet conditions, the stopping distance will be longer by the distance covered during the driver's reaction time.
Considering constant velocity during the reaction time, the car travels 15.0 m while the driver reacts, making the total stopping distance 15.0 m greater than without taking reaction time into account.
Therefore, the correct answer is option a. On a wet road surface starting at about 35 mph.