How to Calculate Friction
What is Friction?
Friction is the force resisting relative motion between surfaces. Static friction prevents motion from starting; kinetic friction acts during motion. Friction force = coefficient of friction (μ) × normal force (N). Higher μ means more friction.
Step-by-Step Guide
- 1F_friction = μ × N (normal force)
- 2Static friction (max): μₛ × N (before motion starts)
- 3Kinetic friction: μₖ × N (during sliding, usually μₖ < μₛ)
- 4Normal force = weight × cos(θ) on an incline at angle θ
Worked Examples
Input
10 kg box, μ = 0.4, flat surface
Result
F_friction = 0.4 × 98.1N = 39.2 N
Normal force = mg = 10 × 9.81
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