Friction Coefficient Calculator

Find the friction coefficient for known normal force and friction using the friction coefficient calculator.

Coefficient needed to hold this slope0.364yours is enough

Friction force184.3047 N0.4 × 460.762 N normal force

Normal force460.7618 Nweight × cos 20°

Weight490.3325 N

Component down the slope167.7036 Nweight × sin 20°

Net force-16.6011 Nfriction holds it — it stays put

Force still needed to move it16.6011 N

Angle at which it starts to slide21.801°arctan of the coefficient — independent of mass entirely

Work done against friction per metre184.3047 Jall of it becomes heat

The formula

F = µN, with N = mg cos θ on a slope

Area does not appear, and neither does mass

Friction is proportional to the force pressing the surfaces together, not to how much of them touch. A wide tyre and a narrow one of the same rubber, under the same load, generate the same friction in the simple model. Real tyres are more complicated, but the first-order result is genuinely area-independent.

The angle at which an object begins to slide is arctan µ, with no mass term at all — because increasing the mass raises the driving component and the friction in exactly the same proportion. A heavy crate and a light one of the same material slide at the same angle, which is a reliably surprising result.

Static friction is usually larger than kinetic, so more force is needed to start something moving than to keep it moving. That is the jerk you feel when a stuck drawer finally gives, and it is why this page takes a single coefficient: use the static value to ask whether it moves, and the kinetic value to ask how fast.