Friction:

Advantages of friction:

 1 Friction enables us to walk freely.

2 It helps to support ladder against wall.

3 It becomes possible to transfer one form of energy to another.

4 Objects can be piled up without slipping.

5 Breaks of vehicles work due to friction.

Disadvantages of friction:

1 It always resists the motion, so extra energy is required to overcome it.

2 It causes wear and tear of machines.

3 It decreases the life expectancy of moving parts of vehicles.

4 Since friction is very useful in some cases while harmful in some cases, friction is called a necessary evil.