Friction is the force that opposes the relative motion between two surfaces in contact with each other. It arises due to bumps and imperfections at the microscopic level between the two surfaces that cause them to stick together. There are two types of friction: static friction that acts before motion occurs, and kinetic friction that acts once motion has started. Friction is both helpful in many applications like walking and writing, but also causes inefficiencies in machines by converting useful energy into heat and causing wear and tear of moving parts over time. Engineers try to control friction through measures like changing surface roughness, adding grooves or spikes, or using lubricants.

1. FRICTON

3. Suppose you decide to ride a skate board
You push off the ground and start moving
According to Newton’s second law
of motion ,if no
other forces are acting
on your skateboard , you
will continue to move….BUT

4. The reason is that there exist a force
between the
ground and lower portion of the
skateboard, called
FRICTIONAL FORCE.

5. Friction is the force which opposes relative
motion
between two surfaces in contact with each
other

6. Even though a surface may look smooth, if you magnify the
surface it isn’t smooth.
Everything is made of molecules. The molecules come
together to make bumps. Some surfaces have molecules
that leaves large bumps and some leaves small bumps.
Micro welds occur when two bumpy surfaces are rubbed
up against each other they stick together.

7. Static friction
Frictional force between two surfaces before there
is a relative force between the surfaces in contact.
Kinetic friction
It is the force of friction which calls in to play
when there is relative force between the surfaces.

9. Helps us in walking conveniently. It save us from
slipping.
Helps us in writing on piece of paper.
Helpful in eating and drinking
Lighting a match stick by rubbing.
Nails and screws join two surfaces due to the
friction.
 we can not climb a tree.
Trains can run on the rails.
In fact life become impossible if there is no friction
in nature.

10. Due to friction the whole energy given to a machine is
not converted in to useful work; a portion of energy is
wasted to overcome friction.This reduces the
efficiency of the machine. The energy used in
overcoming friction appears as heat. Moreover,
friction causes wear and tear of the moving parts of
the machine due to rubbing.

12. It is not possible to walk or drive through muddy
and slippery roads. For this sand and gravels are
spread to reduce friction
 Tyres of our vehicles also the soles of the shoes are
grooved.

Mountaineers also wear spiked shoe.
To overcome skidding along a slippery surface we adopt
measures to increase friction.

13. •Reduce the area of contact of two surfaces.
•Making the surfaces as smooth.
•Lubrication can reduce friction.
•Using ball bearings.