Friction is a contact force that acts opposite to the motion or tendency of motion of two surfaces in contact. It arises due to interlocking of irregularities on the surfaces when one moves over the other. There are three main types of friction: static friction between non-moving surfaces, sliding friction between moving surfaces, and rolling friction between a rolling object and surface. Friction has both advantages, such as allowing movement, and disadvantages, such as causing wear and generating heat. It can be controlled to some degree by lubrication, surface smoothness, and other factors.

1. Friction
Efforts by :Aagman Saini

2. Friction is a contact force that tends to stop a moving
and also tends to stop a stationary object from moving.
The force of friction acts in a direction opposite to the
direction of a motion of an object.
Introduction

3. Every surface has irregularities no matter how smooth it
is. When one surface moves over another, the
irregularities get interlocked with each other. This slows
down the motion. This is the cause for friction.
Factors affecting friction

4. There are 3 types of friction
 Static friction
 Sliding friction
 Rolling friction
Types of friction

5. When the frictional force between the two surfaces is
maximum it is called static friction.
Static Friction

6. Sliding friction is the force of friction between two
surfaces when one surface is actually moving over
another. It is less than static force.
Sliding Friction

7. Rolling Friction is the force of friction between two
surfaces when one surface rolls over another.
It is less than sliding friction.
Rolling Friction

8.  Without friction we would slip & fall every time we
attempt to run or walk.
 Friction causes nails and screws to hold on walls.
 Car and buses are able to run on roads because
friction is present between tyres and roads.
 Without friction, writing on paper would be
impossible the tip of pen would slip on paper.
Advantages of Friction

9.  Energy is wasted in overcoming the force of friction.
 Friction produces heat because energy is wasted in
overcoming friction gets converted into heat.
 Forest fires are caused due to friction between
branches of trees.
 Friction causes wear & tear of tyres and soles of
footwear as they rub each other.
Disadvantages of Friction

10. Friction can be minimised in several way:
 It can be reduced by using a suitable lubricant like oil
and grease.
 It can be reduced by using ball bearings.
 It can be reduced by making the rubbing surfaces
smooth by polishing them
Minimising friction

11. Friction can be increased in the following ways:
 It can be done by making the surfaces rough
 Sand and gravel is strewn on slippery ground during
rainy season to increase friction to walk easily.
 Tyres have grooves to increase friction.
Increasing friction