Friction is a contact force that opposes the relative motion between two objects in contact. It can slow objects down or prevent stationary objects from moving. Friction depends on the nature of the surfaces in contact, with rougher surfaces producing more friction than smoother surfaces. Friction has both advantages, like allowing us to walk and brake vehicles, and disadvantages, such as causing wear and generating heat that can damage machines. The level of friction can be controlled by changing surface roughness, using lubricants, or altering pressure between surfaces.

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2. FRICTION
BY GROUP NO. 3

3. What is friction?
#FRICTION
is a contact force that slows
down moving objects or
prevents stationary objects
from moving.

4. Examples of Friction
• A washing machine pushed along the floor.

5. *Rubbing both hands together
to create heat.

6. A person sliding down a slide.

7. Frictional force always opposes the
motion of an object

8. Friction prevents movement until the force
applied is greater than frictional force
FRICTION

9. Rough and smooth surfaces
• Rough surfaces have
grooves and ridges
• Smooth surfaces are
polished and glossy

11. FRICTION ON SMOOTH AND
ROUGH SURFACES
When rough surface moves over
another, grooves and ridges on rough
surfaces get caught up. This causes
friction. While grooves and ridges
aren’t present on smoother surfaces
and not much friction is produced.

14. SPRING BALANCE
Spring Balance is a
device that measures
force. It uses the
principle that the
greater the force, the
greater is the
extension that the
force produces in a
coiled spring.

15. FRICTION TESTER

16. DEPENDENCE OF FRICTION ON HOW
HARD THE SURFACES PRESS TOGETHER
ROUGH SURFACE ROUGH SURFACE
Friction is lower Friction is higher

17. The friction is more when
we press down because the
interlocking irregularities
increases when we press
the two surfaces harder
together.

18. HENCE.........
* Friction depends on the nature of the surface
in contact.
* France depends on the mass of the moving
object.

19. FRICTION IN DAILY LIFE

20. ADVANTAGES OF FRICTION
• It is because of friction
between our feet or
shoes and the ground
that we are able to walk
by pushing our feet
against the ground.
Without friction, we
would slip as soon as
we tried to walk.

21. • It is very
difficult to walk
on ice or on a
very smooth
and polished
floor. This is
because the
friction between
our shoes and
these surfaces is
very little.

22. • Cars and buses are able to move safely on
the road because of friction between the
treaded tyres and the surface of the road.

23. • Brakes on cycles or cars work because of
friction. When brakes are applied, the ‘shoes’
of the brakes rub against the wheels. The
friction between them reduces the speed.

24. • It would not be possible to light a matchstick
by rubbing it against the matchbox if there
was no friction.

25. • We can write on paper due to the friction
between the pen or pencil and paper.

26. • Friction causes nails and screws to hold
on to walls.

27. DISADVANTAGES OF FRICTION
• Friction causes waste of energy because any
object that moves, has to overcome the
force of friction.

28. • Friction wears out the rubbing surfaces. The
soles of shoes wear out in a few months due
to friction.

29. • Friction generates heat which can be
harmful. The heat produced in a fast-moving
machine is very high. Proper arrangements
have to be made to cool the machine,
otherwise it can get damaged.

30. MINIMIZING FRICTION
• Since, friction is
due to
roughness of
surfaces, any
process that
makes the
contact surfaces
smooth will
reduce friction.

31. • By Polishing

32. • By lubrication

33. • By streamlining to reduce fluid friction

34. DRAG and AIR RESISTANCE
• The frictional force
that fluids exert on
objects is called
drag.
• The bodies of
aeroplanes, missiles,
rockets, cars are
streamlined to
reduce friction with
air, called Air
Resistance.

35. • By using wheels and ball bearings

36. Rolling friction
• When a spherical or cylindrical object rolls on
a surface, the resistance it encounters is called
ROLLING FRICTION.

37. Sliding Friction
• The resistance that an object encounters
when it slides over a surface is called SLIDING
FRICTION.

38. Rolling friction is less than Sliding
friction
* It is not possible to reduce friction to zero, as
no surface is absolutely smooth.

39. INCREASING FRICTION
• It is sometimes desirable to increase friction
to avoid slipping. Friction can be increased by
making the surfaces rough.

40. • Tyres have designs and patterns with grooves
on the surface to increase friction with the
road.

41. • Sand and gravel is strewn on slippery ground
during the rainy season to increase friction.

42. • Spikes are provided in the soles of shoes used
by players and athletes to increase friction so
that they get a firm grip on the ground.

43. • Gymnasts apply a coarse substance on their
hands to improve their grip.

44. QUESTION TIME
Q1) Is force everywhere ?
Explain through 3 examples.

46. Q2) Ram pushes a box of 8 kg and
Ramesh pushes a box of 7 kg with a
box of 3 kg kept above the other box.
Ramesh faces more problem in pushing
the boxes. Why is it so? Explain.

47. Q3) Why
do you
think it's
difficult
to walk
on ice?

48. CREDITS
• ANAGHA
• YATHARTH
• ASHVIK
• ANSHUMAN
• ARYAN
• ISHAAN
• MANSHA