---
title: "Coefficient of Kinetic Friction — AP Physics C Definition"
description: "The coefficient of kinetic friction (μk) relates sliding friction to normal force via f_k = μkN. See how it shows up in AP Physics C dynamics and energy FRQs."
canonical: "https://fiveable.me/ap-physics-c-mechanics/key-terms/coefficient-of-kinetic-friction"
type: "key-term"
subject: "AP Physics C: Mechanics"
---

# Coefficient of Kinetic Friction — AP Physics C Definition

## Definition

The coefficient of kinetic friction is a value that represents the amount of force required to keep two surfaces sliding against each other at a constant velocity.

## Related Study Guides

- [2.1 Newton's Laws of Motion: First and Second Law](/ap-physics-c-mechanics/unit-2/newtons-laws-motion-first-second-law/study-guide/Wt9a5Y5AqCUr4TVnFX4i)

## Review

### Related Terms

- [Coefficient of Static Friction](/ap-physics-c-mechanics/key-terms/coefficient-of-static-friction): The coefficient of static friction is a value that represents the amount of force needed to overcome static friction and initiate motion between two surfaces.
- Normal Force: The normal force is the perpendicular force exerted by a surface on an object in contact with it.
- [Frictional Force](/ap-physics-c-mechanics/key-terms/frictional-force): Frictional force is the force that opposes motion between two surfaces in contact with each other.