Which type of friction is encountered when an object is sliding across a surface?

The scenario described involves an object sliding across a surface, which specifically relates to the forces acting on it during motion. The type of friction that is encountered in this situation is kinetic friction, also known as dynamic friction. This frictional force opposes the motion of the object as it moves along the surface.

Kinetic friction occurs when two surfaces are in relative motion, and it typically has a lower coefficient than static friction, which is the friction that must be overcome to start an object moving from rest. Therefore, once the object is already sliding, kinetic friction is the relevant force to consider.

While static friction is associated with an object that is not moving and must be overcome to initiate motion, inertial friction is not a standard term in mechanics and does not apply to this context. Dynamic friction is sometimes used interchangeably with kinetic friction but is less precise than the term kinetic friction, which is more commonly used in physics to describe friction during sliding motion. Thus, choosing kinetic friction as the answer specifically identifies the type of friction acting while the object is sliding across the surface.