Dual Nature of Friction in Daily Life:

Friction, often considered an impediment, is a ubiquitous force with dual characteristics—both obstructive and indispensable. While it resists motion, causing wear and energy loss, it is essential for traction, grip, and many everyday processes. Understanding and managing this paradoxical force are vital for optimizing efficiency and functionality in various fields.

Positive Force in Daily Activities:

Can we imagine our daily activities without the essential role of friction?

• 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.

Undesirable Consequences: Wear, Heat, and Energy Loss Caused by Friction

• 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.

What influences the Increase or Reduction of Friction?

•  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.

Wheels Reduce Friction: Power of Rolling

• 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.

Fluid Friction: Design, Drag and Efficiency

• 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. 

Conclusion

• The physical world operates on a series of interconnected principles. The relationship between force, pressure, and friction provides a foundation that determines how objects move and interact.