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Positive Force in Daily Activities: Can we imagine our daily activities without the essential role of friction?
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- Friction is essential for many of our daily activities. It allows us to grip objects, like a glass or an earthen pot.
- If these objects were greasy, it would be harder to hold them because resistance would be reduced.
- Walking would be nearly impossible without resistance, as evidenced by the difficulty we face on slippery surfaces.
- Writing with pen, pencil, or chalk requires resistance between the writing instrument and the surface.
- Resistance between the tires of vehicles and the road allows them to start, stop, and turn.
- Building and construction activities, like fixing a nail on the wall or tying a knot, depend on resistance.
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Undesirable Consequences: Wear, Heat, and Energy Loss Caused by Friction
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- It causes wear and tear of materials, such as screws, ball bearings, shoe soles, and even infrastructure like the steps of over-bridges at stations.
- It can produce heat, leading to energy wastage. For example, when palms are rubbed vigorously, they feel warm.
- Striking a matchstick produces fire due to resistance to heat. Similarly, machines like mixers heat up due to resistance, causing energy losses.
 [Soles of shoes wear out due to friction]
 [Rubbing of your palms makes you feel warm]
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What influences the Increase or Reduction of Friction?
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- Art and Science of Increasing Friction in everyday activities: In many situations, increased resistance is beneficial, such as:
- Shoe soles and tires are grooved or treaded to provide better grip with the ground.
- Brake systems in vehicles use resistance to stop movement.
- Kabaddi players and gymnasts use soil or coarse substances, respectively, to enhance grip by increasing resistance.
- Strategies and techniques for Reducing Friction in various applications: There are instances when it’s desirable to decrease resistance:
- Fine powder on a carrom board makes the striker and coins move smoothly.
- Lubricants like oil, grease, and graphite are used to reduce resistance between machine parts, forming a layer that prevents direct surface-to-surface contact.
- This avoids the interlocking of surface irregularities, resulting in smoother movement.
- In cases where traditional lubricants might not be suitable, other methods like air cushions between moving parts are used to reduce resistance.
 [Action of lubricant]
 [Motion of the book on rollers]
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Wheels Reduce Friction: Power of Rolling
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- Wheels are one of humanity’s most impactful inventions, mainly because they significantly reduce resistance.
- When an object rolls over another, the resistance is termed “rolling friction,” which is usually much less than “sliding friction.”
- This is illustrated by the ease with which a book moves over cylindrical pencils placed parallelly under it, rolling them forward.
- Similarly, heavy machinery is sometimes moved by placing logs underneath, allowing it to roll.
- Luggage with wheels or rollers exemplifies the advantage of rolling over sliding. By reducing resistance, rolling makes it much easier to transport even heavy loads.
- This principle is implemented in machines using ball bearings, which replace sliding with rolling, thus reducing resistance and wear.
- Common applications of ball bearings include the hubs and axles of ceiling fans and bicycles.
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Fluid Friction: Design, Drag and Efficiency
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- Despite being thin and light, fluids, which encompass both gases (like air) and liquids, exert resistive forces on objects moving through them.
- This resistive force exerted by fluids is termed “drag.”
- The amount of drag an object experiences in a fluid depends on:
- Its speed relative to the fluid.
- The shape of the object.
- The nature of the fluid.
- To ensure efficiency and minimize energy loss due to resistance, objects are designed to have streamlined shapes that reduce fluid friction.
- Nature provides numerous examples of optimal shapes to minimize drag.
- Birds and fishes, which navigate through fluids continuously, have evolved streamlined body shapes to efficiently overcome resistance.
- Drawing inspiration from nature, engineers design vehicles, especially aircraft, with shapes that minimize drag, making them more energy-efficient and faster.
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 Rolling reduces friction
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 Ball bearings reduce friction
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