Calculator · Engineering Mechanics
Static Friction Calculator
Compare the tangential force a body needs for equilibrium with the largest friction force the contact can supply, F ≤ μs·N.
Contact
Compression only: N ≥ 0.
Signed along the tendency of motion; friction opposes it.
Results
| Maximum static friction F_max = μs·N | 70 N |
|---|---|
| Required friction |F| | 50 N |
| Friction actually developed | -50 N |
| Remaining margin F_max − |F| | 20 N |
| Utilisation |F| / F_max | 0.71429 |
| State | Sticking — static equilibrium holds |
Diagnostics
- · Info Below the limit the friction force follows from equilibrium, not from μs·N: it is exactly the force needed to hold the body, acting opposite the tendency of motion.
Technical reference
|F_f| ≤ μs·N
|F_f| = μs·N (impending slip only)
- F_f
- friction force actually developed at the contact[N]
- μs
- coefficient of static friction[–]
- N
- normal contact force[N]
μs·N is the MAXIMUM AVAILABLE static friction, not the friction force itself. Below that limit the friction actually developed equals the REQUIRED tangential force from equilibrium, with the opposite sign — this tool reports the two separately rather than conflating them.
“Sticking” holds while the required force stays under the limit; “impending slip” is the equality case |F_f| = μs·N; beyond the limit the state is “static equilibrium impossible” and no friction value is reported, since the body must slide.
Assumptions
- · Coulomb dry friction at a single planar contact: the developed friction equals the equilibrium demand until it reaches μs·N.
- · Below the limit the friction force is whatever equilibrium requires — it is not μs·N.
- · At the limit the state is impending slip; beyond it no static equilibrium exists and no friction value is reported.
- · Kinetic friction, rolling resistance and surface deformation are outside this tool.
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