Write some methods to both increase and decrease friction.

Explanation

As friction is both harmful and useful to us it is important to know some methods to increase or reduce friction as per our need.
Some methods to increase friction are :
Friction can be increased by making the surfaces in contact uneven or rough. This can be done by :
(i) Creating grooves and treads on the rubbing surface, e.g.,
Grooves on the sole of shoes
Treads on the tyres of vehicles
Break pads in the brake system of bicycles.
(ii) Applying a coarse substance on the rubbing surface, e.g.,
Kabaddi players rub their hands with soil.
Gymnasts apply a coarse substance on their hands.
Some methods to reduce friction are : Friction can be reduced by making the surfaces even or smooth. This can be done by :
(i) Polishing or smoothening the rubbing surfaces.
(ii) Adding a thin layer of oil grease or powder on the surface, e.g.,
Sprinkling powder on the carrom board.
Applying oil to the door hinge.
Lubricating or greasing the moving parts of machines.
Using ball bearing in machines