State two situations for which friction is considere
to be:
desirable
undesirable

(α) Desirable Friction

1. Walking or Running:
   • Explanation: The friction between your footwear and the ground provides the necessary grip to push off the ground, enabling movement without slipping. Without sufficient friction, walking or running would be unstable and potentially dangerous.
2. Braking Systems in Vehicles:
   • Explanation: Friction between the brake pads (or shoes) and the wheels (or brake discs/drums) is essential for slowing down or stopping a vehicle. This controlled friction converts the vehicle’s kinetic energy into heat, allowing for effective deceleration.

(β) Undesirable Friction

1. Engine Components:
   • Explanation: In engines, friction between moving parts like pistons, cylinders, and bearings leads to energy losses and generates unwanted heat. This not only reduces the engine’s efficiency but also contributes to wear and tear, potentially shortening the engine’s lifespan.
2. Machinery and Mechanical Systems:
   • Explanation: In various mechanical systems, excessive friction can cause parts to wear out prematurely, increase energy consumption, and generate unwanted heat. For example, in industrial machinery or household appliances, reducing friction through lubrication or material selection is often necessary to enhance performance and longevity.

Additional Notes

• Managing Friction: While some applications benefit from friction, others require its reduction. Engineers often use lubricants, bearings, and other technologies to manage friction levels appropriately based on the desired outcome.
• Material Selection: The choice of materials in different components can influence the amount of friction. For instance, using rubber for tires increases friction with the road, enhancing grip, whereas using polished steel in engines minimizes unwanted friction.