Final answer:
The coefficient of kinetic friction (μk) is the ratio of the force of kinetic friction to the normal force acting on an object, playing a crucial role in the motion of objects on various surfaces. It is used to calculate the force necessary to maintain motion, like a skier sliding down a slope or a crate being pushed on a flat surface, and changes based on surface characteristics and lubrication.
Step-by-step explanation:
The coefficient of kinetic friction is significant because it represents the ratio of the force of kinetic friction to the normal force acting on an object.
Given that the magnitude of kinetic friction is 45.0 N and there is no acceleration, the kinetic friction and the component of the skier's weight down the slope are balanced. Hence, we can apply the equation μk mg cos θ = mg sin θ to find the coefficient of kinetic friction.
If we consider a scenario with a 100 kg crate on a flat surface, we can determine the normal force as the weight of the crate (W = mg = 980 N), which acts perpendicular to the floor. Knowing the coefficient of static friction (μs = 0.45) or kinetic friction (μk = 0.30), the respective forces necessary to start and maintain the motion can be calculated (440 N to initiate motion and 290 N to maintain constant velocity).