To increase friction, surfaces must be made rough so they interlock, and be pressed harder against each other. Examples include brake pads that arrest the motion of wheels through friction when the brake lever is pressed, and kabaddi players or gymnasts applying coarse substances to their hands to improve their grip. To reduce friction, a lubricant can be added between surfaces to form a thin layer so the surfaces do not directly rub against each other, avoiding interlocking of irregularities and allowing for smoother movement.

1. To reduce friction we can make the surfaces in
contact smooth. Also adding lubricant to two
surfaces in contact reduces the friction between
them .
To increase friction the surfaces in contact had to
be made rough. The two surfaces in contact had to
be press harder to increase the friction .

2. Examples of increased friction

3. Example of reduced friction

4. HOW TO INCREASE FRICTION
We deliberately increase friction by using brake pads on
braking system of bicycles and automobiles.
When you are riding an automobile the brake pads do
not touch the wheels until you press the brake lever these
pads arrest the motion rims due to friction .the wheels
stop moving .
Other examples are kabaddi players rub their hands into
sand to get better grip , gymnast apply some coarse
substance on their hands to get better grip .

5. HOW TO REDUCE FRICTION
The main way to reduce friction is to add lubricants
between the substances when these are applied
between the moving part of the machine , a thin layer
is formed and the moving parts are not ddirectly rub
agaisnt each other .interlocking of irrregularities is
avoided to great extent . Movements become smooth.