Final answer:
The grip necessary for a vehicle to start, stop, and change direction is provided by the friction between the tires and the road surface. This friction provides the centripetal force needed to maintain control, especially during turns, and is essential for vehicle stability on curves. Rolling without slipping indicates static friction at the contact point of the tires, highlighting its key role in vehicle traction.
Step-by-step explanation:
The grip between tires and the road surface is critical for a vehicle to start, stop, and change direction. This grip is provided by the aid of friction between the tires and the road. In physics, friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. Without sufficient friction, the vehicle cannot harness the necessary net external force to produce the needed horizontal centripetal force to navigate curves safely.
When a vehicle turns on a curve, the force that keeps it from sliding out is centripetal force, which is directed toward the center of the circular path. The ideal speed mentioned refers to the maximum speed at which a car can navigate a turn safely without relying solely on friction, that is, considering factors like the banking of the curve. However, on typical roads, the friction between the tires and the road is necessary to maintain traction and control during turns, especially at higher speeds.
An example is during icy road conditions where winter tires, designed to create more friction on slippery surfaces, are preferred over summer tires. This difference in tire design highlights the importance of appropriate tire-road friction in maintaining vehicle stability on curves. Moreover, the concept of rolling motion without slipping reveals that when a vehicle is moving and its wheels are turning at a rate matched to its speed (rolling without slipping), the contact point of the tires with the road is momentarily at rest, meaning there's static friction acting instead of kinetic friction.