1)Friction is used to pull a roller on the ground than to push it because friction b/w. the roller and ground is less in pulling the roller. 2) It is due to friction that the trains and cars move , otherwise wheels would have rotated at one place only. 3) Friction makes it possible to write on paper with the pencil.
Disadvantage of friction :-
1) Friction cause wear and tear of moving parts of the machine. 2) Friction reduces the efficiency of machine.
Answers & Comments
1)Friction is used to pull a roller on the ground than to push it because friction
b/w. the roller and ground is less in pulling the roller.
2) It is due to friction that the trains and cars move , otherwise wheels would have rotated at one place only.
3) Friction makes it possible to write on paper with the pencil.
Disadvantage of friction :-
1) Friction cause wear and tear of moving parts of the machine.
2) Friction reduces the efficiency of machine.
hope its help