Question

Give examples to show friction is both a friend and a foe.

Answer 1

We need to define friction and state its advantages to prove why it is our friend. And then we need to state the disadvantages to show that friction can also become our foe.

Complete answer:
Friction is defined as the resistance to motion of one object moving relative to another.
It is to be noted that friction is not a fundamental force, like gravity or electromagnetism. Instead, scientists believe it is the result of the electromagnetic attraction between charged particles in two touching surfaces. Friction plays an important part in many everyday processes, thus it is a necessary evil.
Stated below are the advantages of friction which show that friction is our friend.
Friction allows us to grip and catch different objects.
It helps us to walk comfortably on the surface. It helps to minimise the speed or to stop the moving objects.
When two objects are rubbed together, friction causes some of the energy of motion to be converted into heat. This is why rubbing two sticks together will eventually produce a fire.
Friction also helps us to write on paper or blackboard.
Stated below are the disadvantages we face due to friction. This shows why friction is foe :
Friction causes wear and tear in objects.
It damages the parts of machines. The machines or tools require regular maintenance due to which a lot of money is wasted.
It reduces the speed of moving objects so more force is required. Since friction keeps things in place, it does not allow the free movement of objects.

Note:
For every general rule about friction, there are just as many exceptions. For instance, while two rough surfaces (such as sandpaper) rubbing against each other sometimes have more friction, very smoothly polished materials (such as plates of glass) that have been carefully cleaned of all surface particles may actually stick to each other very strongly.