Friction
Physics · घर्षण
📋Quick Overview
Friction is the force that opposes the relative motion between two surfaces in contact. When you push a box on the floor, friction is what makes it hard to push. Without friction, you couldn't walk, write, or hold anything! Friction always acts opposite to the direction of motion.
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Friction is caused by the irregularities (roughness) of surfaces. Even smooth-looking surfaces have tiny bumps at the microscopic level. These bumps interlock and resist motion.
📖Types of Friction
| Type | When it Acts | Magnitude | Example |
|---|---|---|---|
| Static Friction | When object is at rest but force is applied | HIGHEST (hardest to start motion) | Pushing a heavy almirah — hard to start moving |
| Kinetic/Sliding Friction | When object is sliding on surface | LESS than static friction | Pushing a box that is already moving on floor |
| Rolling Friction | When object rolls on surface | LEAST of all (easiest motion) | Wheels of a car, ball rolling on ground |
| Fluid Friction | When object moves through liquid or gas | Depends on speed & shape | Swimming in water, airplane in air |
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Key order: Static > Kinetic/Sliding > Rolling. That's why it's harder to START pushing a box than to KEEP it moving. And wheels (rolling) make it even easier!
📖Advantages & Disadvantages of Friction
📝Methods to Reduce & Increase Friction
- •REDUCE friction: Use lubricants (oil, grease), use ball bearings, polishing surfaces, streamlining shapes (cars, planes, boats)
- •REDUCE friction: Use wheels (rolling friction << sliding friction)
- •REDUCE friction: Use powder (talcum powder on carom board)
- •INCREASE friction: Make surface rough (treads on tyres, sandpaper on shoes)
- •INCREASE friction: Sprinkle sand on slippery roads
- •INCREASE friction: Use brake pads (rough material)