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Kumar Rohan
Physics and Mathematics
Friction — Complete Formula
- ⭐ – Most used in JEE
- ⚠️ – Common Mistake
- 💡 – Memory Hint
Friction
| Concept | Formula | Symbols Meaning | SI Units | Key Notes / Tricks |
|---|---|---|---|---|
| Static Friction | [f_s \leq \mu_s N] | [f_s] = static friction, [μ_s] = coefficient, N = normal reaction | N | Self-adjusting ⚠️ |
| Limiting Friction | [f_{max} = \mu_s N] | [f_{max}] = maximum static friction | N | Just before motion ⭐ |
| Kinetic Friction | [f_k = \mu_k N] | [f_k] = kinetic friction, [μ_k] = coefficient | N | Constant during motion |
| Angle of Friction | [\tan\theta = \mu] | θ = angle of friction, μ = coefficient | — | Useful in incline problems |
| Angle of Repose | [\tan\theta = \mu] | θ = angle of repose | — | Same as friction angle ⭐ |
💡 Memory Hint:
Static → varies
Kinetic → fixed
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