What is the difference between static and kinetic friction?

Static friction resists the start of motion up to a limit; kinetic friction acts after surfaces slide.

Does the coefficient of friction have units?

No. It is a dimensionless ratio between friction force and normal force.

No. It is an ideal physics model and does not replace road, tire or safety engineering analysis.

Calculate friction force, static or kinetic friction, incline behavior, ideal sliding distance and the sliding angle.

What to calculate

Horizontal surface Incline Braking distance Sliding angle

Mass

Surface preset

Static friction coefficient μₛ

Kinetic friction coefficient μₖ

External force (pull magnitude)

✗ Body stays at rest because the applied force is not enough to break static friction

Normal force N

14,710 N

Max static friction F_max

13,239 N

Friction force F_f

3,000 N

Acceleration a

0 m/s²

Force unit:

Normal force for mass 1,500 kg: 14,710 N.

Static friction limit at coefficient 0.9: 13,239 N.

Kinetic friction at coefficient 0.7: 10,297 N.

The English SERP centers on, often with static and kinetic friction separated.

f = μ N

f is friction force, mu coefficient of friction and N normal force.

f_{s, m a x} = μ_{s} N, f_{k} = μ_{k} N

Static friction has a maximum; kinetic friction applies after sliding starts.

Approximate coefficients

Real friction depends on surfaces, contamination, temperature, wear and loading. Treat presets as rough classroom estimates.

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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