Hint: Frictional force causes a lot of losses in general upkeep and wear and the tearing of machinery. But almost all crucial tasks cannot be carried out without the presence of friction. Basic activities like walking and writing on a surface are possible due to friction. Hence it is considered as a necessary evil.
Friction is a necessary evil because it has both harmful and beneficial effects.
(i) We can walk easily because the ground offers friction. With less friction, the walking situation becomes almost impossible. Therefore, friction is necessary even for a simple task like walking.
(ii) It is a difficult task to move on a wet muddy track, or wet marble floor. This is because these surfaces offer very small friction to the surface of a person's feet.
(iii) Soles of shoes have grooves on them. Grooved soles give more friction to the ground which gives better grip when we walk. Shoes with worn out soles can be slippery.
(iv) Tyres of vehicles have treads for better grip over the road. It provides
friction to the surface of the road. When treads are worn out, the tyres need to be replaced with a new one.
(v) Friction can also produce heat. Vigorously rub your palms together for a few minutes.
(vi) Writing with a pen is possible because paper provides friction to the tip of a pen.
(vii) When a machine is operated, heat generated causes much wastage of energy.
Friction is a force exerted by a surface against the motion of a body across its surface. Frictional forces are the reason why your car comes to a standstill if you don’t accelerate. We see examples all around us where frictional forces act. It is something that we cannot live with and something we cannot live without.