When is friction considered unhelpful in a car?

Friction plays a crucial role in the operation of a car, but there are situations where it can become unhelpful. Skidding on slick surfaces—such as ice or wet roads—demonstrates this concept effectively. When a car skids, the tires lose their grip on the road, meaning that the frictional force, which usually helps control the vehicle’s motion and direction, is significantly reduced. This lack of friction can cause the car to slide uncontrollably, making it difficult for the driver to steer or stop the vehicle effectively.

In contrast, during acceleration or effective braking, friction between the tires and the road surface is essential. It allows the car to transfer the engine's power to the ground or to slow down effectively when needed. Similarly, when moving in a straight line, adequate friction is important for maintaining control and stability. Therefore, skidding on slick surfaces is an instance where friction does not assist and can lead to dangerous situations.