Case 1
- Coefficient of friction (µ)
- 0.3
- Normal force
- 100N
30.000N
Open with these valuesFriction Force Calculator
30.000N
Result: 30.000 NFriction is the coefficient times the normal force, nothing more: µ = 0.3 under a 100 N load gives 30 N. The coefficient is a measured property of the surface pair, not of the object — a large aluminium block has the same µ as a small one, only the load differs.
The numbers at a glance
Held fixed: Coefficient of friction (µ) 0.300.
| Normal force (N) | Result (N) |
|---|---|
| 0.000 | 0.000 |
| 25.000 | 7.500 |
| 50.000 | 15.000 |
| 75.000 | 22.500 |
| 100.000Your value | 30.000 |
| 125.000 | 37.500 |
| 150.000 | 45.000 |
| 175.000 | 52.500 |
| 200.000 | 60.000 |
Worked examples
Case 2
- Coefficient of friction (µ)
- 0.7
- Normal force
- 500N
350.000N
Open with these valuesCase 3
- Coefficient of friction (µ)
- 0.05
- Normal force
- 200N
10.000N
Open with these valuesHow it's calculated
F = µ × N
- StepEnter the coefficient for your surface pair — it has no unit.
- StepEnter the normal force in newtons; on level ground that is the weight.
- ResultRead the friction force in newtons, acting against the motion.
Reference table
| Coefficient, normal force | Surface pair | Friction force |
|---|---|---|
| 0.05, 200 | Ice, a 200 N load on top | 10 |
| 0.3, 100 | A middling dry pair, 100 N | 30 |
| 0.45, 78.5 | An 8 kg block on a rough floor | 35.325 |
| 0.6, 1000 | Steel on steel, dry and clean | 600 |
| 0.7, 500 | Rubber on dry concrete | 350 |
Questions
How do I calculate the friction force?
Multiply the coefficient of friction by the normal force: F = µ × N. With the normal force in newtons the answer is in newtons — µ = 0.3 under a 100 N load gives 30 N.
What is friction force?
It is the resistance that opposes sliding when two surfaces are pressed together and one tries to move across the other. It acts along the surface, opposite to the motion, and is measured in newtons like any other force.
What is the coefficient of friction?
A dimensionless number that captures how grippy a pair of surfaces is, measured rather than derived. Rough guides are 0.7 for rubber on dry concrete, 0.6 for dry steel on steel and about 0.05 for ice. It depends on the materials and their condition, not on the size of the load.
What is the difference between static and kinetic friction?
Static friction resists the start of motion, kinetic friction resists motion once the object is already sliding. The static coefficient is usually a little larger, so it takes more force to break something free than to keep it moving. Use the static value if you want the force needed to start sliding.
What normal force should I enter?
The perpendicular load pressing the two surfaces together, in newtons. On level ground it is the object's weight, so multiply a mass in kilograms by 9.80665. On a slope or under extra push it can be smaller or larger than the weight.
Sources and last check
Information, not professional advice.