Calculadora de Fricção
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
f = μ·N
About this calculator
The Friction Calculator determines the friction force between two surfaces in contact using the formula f = μ·N, where f is the friction force, μ is the coefficient of friction (static or kinetic), and N is the normal force. The calculator allows you to calculate any of the three variables by entering the known values. It is a useful tool for physics students, engineers, and professionals who need to analyze situations involving motion or rest with friction.
The operation is simple: you enter the coefficient of friction (dimensionless) and the normal force (in newtons), and the calculator returns the corresponding friction force. If you want to find the coefficient or the normal force, just provide the other two values. The formula applies to both static friction (which prevents motion from starting) and kinetic friction (which acts during motion), provided the appropriate coefficient is used.
This calculator is ideal for solving high school and college physics problems, such as determining the force needed to move a block on a surface, calculating the deceleration of a vehicle due to friction, or analyzing systems with pulleys and inclined planes. It is also useful in mechanical engineering for designing brakes, conveyor belts, and other systems that rely on friction.
Important precautions: ensure you use the correct coefficient of friction (static or kinetic) for the situation. The static coefficient is usually larger than the kinetic one. The normal force is perpendicular to the contact surface and may differ from weight if there are other vertical forces. Remember that the formula f = μ·N is an approximation; in real cases, friction may depend on other factors such as contact area and speed.
Frequently asked questions
What is the difference between static and kinetic friction?
Static friction acts when the object is at rest and prevents motion from starting. Kinetic friction acts when the object is already moving. The static coefficient is usually larger than the kinetic one.
Can I use this calculator for friction on an inclined plane?
Yes, but you must first calculate the normal force, which on an inclined plane is N = m·g·cos(θ), where θ is the angle of inclination.
What if the coefficient of friction is not provided?
You can use typical tabulated values for common material pairs, such as rubber on asphalt (μ ≈ 0.7) or steel on steel (μ ≈ 0.6).
Does friction force depend on contact area?
In the simplified model (f = μ·N), contact area does not matter. In real situations, there may be some dependence, but for most problems this formula is sufficient.
What unit should I use for normal force?
Use newtons (N). If you enter mass in kg, the calculator may convert to newtons by multiplying by 9.8 m/s², but it is better to provide the normal force directly.