Mechanics
Friction Force
Friction opposes relative motion between surfaces.
Variables
fN
Friction force
Force opposing motion
In SI units: kg·m/s²
Allowed values: 0 or more
μunitless
Coefficient of friction
Dimensionless constant
Allowed values: 0 or more
NN
Normal force
Perpendicular contact force
In SI units: kg·m/s²
Allowed values: 0 or more
Derivation
Empirical relationship. Static: f ≤ μₛN; Kinetic: f = μₖN.
Your notes
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Check value
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- μ = 2 (Coefficient of friction)
- N = 3 N (Normal force)
Result: f = 6 N
Where this formula is listed
- Mechanics formulas, under Dynamics, alongside Hooke's Law, Drag Force, Terminal Velocity, Center of Mass (Two Objects) and Pressure.
- In the mechanics list it comes after Weight and before Hooke's Law.
- Mechanics formula sheet, one of 58 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Friction Force formula?
Friction Force is written f = μN. Friction opposes relative motion between surfaces. It belongs to Mechanics, under Dynamics.
What are the units in f = μN?
In SI units, f is friction force, measured in kg·m/s²; μ is coefficient of friction (dimensionless); N is normal force, measured in kg·m/s².
How is the Friction Force formula derived?
Empirical relationship. Static: f ≤ μₛN; Kinetic: f = μₖN. The result is f = μN.