Final answer:
Friction affects motion not only when solid objects are in contact but also in situations involving fluid friction, rolling friction, and internal friction within deforming materials. It is crucial for activities such as walking, driving, and sports, and is managed with lubricants in mechanical systems.
Step-by-step explanation:
Friction affects motion in various situations apart from just solid objects in contact. For instance, when an object moves through a fluid such as air or water, it experiences fluid friction or drag. This kind of friction also opposes the motion of the object and depends on properties like the object's speed, shape, and the fluid's viscosity. Another example is rolling friction, which occurs when an object rolls over a surface. This type of friction is generally less than sliding friction and affected by the deformations in the rolling object and the surface. Additionally, internal friction or viscous resistance occurs within materials that are deforming, such as when solids are bent or compressed, or when liquids and gases flow.
Other specific scenarios where friction is influential include walking, where the friction between shoes and the ground allows for movement, and vehicle tires gripping the road, which is crucial for safe acceleration and braking. A lack of sufficient friction in these cases can lead to slipping. Moreover, athletes use equipment and clothing designed to minimize friction for enhanced performance, and various mechanical devices incorporate lubricants to reduce harmful friction between moving parts.