Calculate static and kinetic friction from the normal force and coefficient of friction.
Friction depends on the normal force, not the contact area, and on an incline the normal force falls with the cosine of the angle while the sliding component rises with the sine. The object slides when the sine term exceeds maximum static friction. Static friction always exceeds kinetic, which is why an object takes more force to start moving than to keep moving — and why anti-lock brakes exist.
Friction Force
f = μ N, with N = m g cos θ on an incline
f = μ N, with N = m g cos θ on an incline Friction depends on the normal force, not the contact area, and on an incline the normal force falls with the cosine of the angle while the sliding component rises with the sine. The object slides when the sine term exceeds maximum static friction.
Static friction always exceeds kinetic, which is why an object takes more force to start moving than to keep moving — and why anti-lock brakes exist.
This calculator takes 4 inputs: Mass, Static coefficient of friction, Kinetic coefficient of friction, Surface angle from horizontal. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.