What is friction?
PhysicsClass 10CBSEAnswered 25 May 2026
Answer
Friction is the force that resists relative motion between two surfaces in contact. It always acts in the direction opposite to motion or intended motion.
Types of friction:
| Type | Description | Example |
|---|---|---|
| Static friction | Opposes motion before an object starts moving | Pushing a heavy box that does not yet move |
| Kinetic (sliding) friction | Acts while surfaces slide against each other | A book sliding across a table |
| Rolling friction | Resistance when an object rolls on a surface | A ball rolling on a floor |
| Fluid friction (drag) | Resistance in liquids or gases | A swimmer moving through water |
Formula:
Friction force (f) = μ × N
μ = coefficient of friction (depends on surface materials)
N = normal force (force pressing surfaces together)
Friction in daily life:
Useful: Walking (feet grip floor), car brakes, writing (pen grips paper) Harmful: Engine wear, heat buildup in bearings, energy loss in machines
Reducing friction: lubrication (oil, grease), ball bearings, polished surfaces
Increasing friction: rougher surfaces, textured materials (rubber soles)
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