##### Application of Frictional Force

1. Friction acts when two surfaces rub against each other. Friction opposes the movement of objects which rub against one another.

2. Due to frictional force, we need to keep on pedalling a bicycle to keep it going. If we stop pedalling, the bicycle will slow down and stop.

3. Frictional force is important in our daily life. Without frictional force, we cannot walk, run or carry out our daily activities.

Application Of Increased Friction

1. Frictional force can be increased by increasing the roughness of contact surfaces.

2. We need to increase friction to

(a) slow down moving objects more quickly

(b) hold things more firmly

(c) grip surfaces better

3. The applications of increased friction:

(a) Rubber pads or knobs are fixed to the bases of many household appliances like
telephones, televisions, electrics kettles and rice cookers to prevent them from
slipping while in use.

(b) Tyres and shoes are given deep treads or grooves for a good grip on slippery surfaces.

(c) Brake pads are used on wheels to slow down or stop vehicles.

(d) Rough surfaces on staircases and floors prevent us from slipping while walking or
running on them.

Application Of Decreased Friction

1. Frictional force can be reduced by smoothing the contact surfaces.

2. We need to decrease friction to

(a) move things more easily

(b) reduce the hear produced by rubbing parts

(c) slide things over each other more easily

3. The application of decreased friction:

(a) Round and smooth spherical objects like rollers or ball bearings reduce friction.
They are placed around the axles in many machines to allow the axles to turn
smoothly.

(b) A streamlined shape reduces friction, allowing objects to move easily through liquids
and
gases. Cars are usually tested in a wind tunnel for a streamlined body design.
A high-speed trains has a streamlined shape for smooth movement through air.

(c) A layer of air between two contact surfaces reduces friction. The layer of air between
the hull of a hydrofoil and the water allows the hydrofoil to move at high speeds.

(d) A conveyor belt moves on wheels or rollers to reduce friction. It is used in airports to
transport luggage and in factories to move good and heavy objects.

(e) Lubricants such as oil and grease can reduce friction when applied between contact
surfaces. Lubricants are also applied on moving parts inside car engines to reduce
friction.