Final answer:
Wheel lock-up occurs when the drive or steer tires stop rotating during braking due to excessive brake force overcoming the tires' traction. This can lead to a loss of steering control and increased stopping distance, which anti-lock braking systems (ABS) aim to prevent.
Step-by-step explanation:
When the drive or steer tires have stopped rotating under braking, this is known as wheel lock-up. This situation occurs when the force applied to the brake system exceeds the tire's ability to maintain traction with the road surface, causing the tires to cease rotation and effectively skid along the surface. The outcome can be a loss of steering control and an increase in stopping distance, which is why modern vehicles are equipped with anti-lock braking systems (ABS) to prevent this scenario.
It is important to distinguish between the various terms associated with driving dynamics:
- Understeer occurs when the front wheels do not turn as much as intended, which usually happens when cornering at high speeds, resulting in the vehicle continuing in a straighter line than desired.
- Wheel slip is related to the wheels losing traction, but this can happen under acceleration or braking, and it does not necessarily mean complete cessation of rotation as with wheel lock-up.
- Oversteer is when the rear wheels slide outwards during a turn, potentially causing the rear of the vehicle to swing around in a fishtail motion.
Therefore, the correct option in the final answer to what occurs when the drive or steer tires have stopped rotating when braking is c) Wheel lock-up.