1. Made By:
Nikhil Gupta
XI A

2. 1. Force
2. Newton’s 1st law of Motion
3. Inertia
4. Types of Inertia
5. Momentum
6. Newton’s 2nd law of Motion
7. Impulse
8. Newton’s 3rd law of Motion
9. Law of Conservation of Momentum
10. Applications of Newton laws of Motion

3. 11. Friction – A necessary evil
12. Cause of Friction
13. Types of Friction
14. Laws of Limiting Friction
15. Coefficient of Friction
16. Angle of Friction & Angle of Repose
17. Advantages & Disadvantages of Friction

4. Force :
 It is an external agency which
changes or tends to change the
state of motion or direction of its
motion or the shape of an object is
known as force.
 In layman’s term it is also known as
push or pull applied on an object.

5. *Acc. to newton’s 1st law of motion, an
object continues to be in its state of rest
or state of motion along a straight line
until and unless an external unbalanced
force is applied to it.
*It is also known as law of inertia.
*It also defines force

6. INERTIA
It is that inherent property of a
material body by the virtue of which it
resists any change in its state of rest or
of uniform motion along a straight
line.

7. Types of inerTia
1. Inertia Of Rest: An Object Tends To Be In
State Of Rest Until & Unless An External &
Unbalanced Force Is Acted Upon It.
2. Inertia Of Motion: It Is That Inherent Property
Of A Material By Virtue Of Which It Resists
Any Change In Its State Of Motion.
3. Inertia Of Direction: It Is A Inherent Property
Of A Material By Virtue Of Which It Resists
Any Change In Its Direction Of Motion.

8. These pumpkins will not move unless
acted on by an unbalanced force.

9. Once
airborne, this
ball would not
stop unless
acted on by
an unbalanced
force (gravity
and air – fluid
friction), it
would never
stop!

10. Why then, do we observe
every day objects in
motion slowing down and
becoming motionless
seemingly without an
outside force?
It’s a force we sometimes
cannot see – friction.

11. Momentum

12. NewtoN’s 2Nd Law of MotioN
 It states that the rate of change of
momentum is directly proportional to the
force applied and change takes place in
the direction of force applied
 Alternatively, it is also stated as the force
is directly proportional to product of mass
and acceleration produced by the force.
F α m*a
F = m*a

13. 2ND LAW
 When mass is in kilograms and acceleration is in
m/s/s, the unit of force is newton (N).
 One newton is equal to the force required to
accelerate one kilogram of mass at one
meter/second2

14. Impulse

15. NewtoN’s 3rd Law of MotioN
 It states that every action has equal and
opposite reaction.
 By newton’s 3rd law of motion
Faction=-Freaction

16. According to Newton,
whenever objects A
and B interact with
each other, they exert
forces upon each
other. When you sit in
your chair, your body
exerts a downward
force on the chair and
the chair exerts an
upward force on your
body.

17.  It states that in an isolated system , the
vector sum of the linear momentum of all
bodies remains conserved and is not
affected by their mutual interaction. i.e.
Initial momentum = final momentum
m1v1+m2v2=(m1+m2)v3

18. Newton's 1st Law
Because of inertia, objects (including you) resist changes
in their motion. When the car going 80 km/hour is stopped
by the brick wall, your body keeps moving at 80 m/hour.

19. Newton’s 2nd Law proves that different masses
accelerate to the earth at the same rate, but with
different forces.
• We know that objects
with different masses
accelerate to the
ground at the same
rate.
• However, because of
the 2nd Law we know
that they don’t hit the
ground with the same
force.
F = ma F = ma
98 N = 10 kg x 9.8 m/s/s 9.8 N = 1 kg x 9.8
m/s/s

20. Newton’s 3rd Law in Nature
 Consider the propulsion of a
fish through the water. A fish
uses its fins to push water
backwards. In turn, the
water reacts by pushing the
fish forwards, propelling the
fish through the water.
 The size of the force on the
water equals the size of the
force on the fish; the direction
of the force on the water
(backwards) is opposite the
direction of the force on the
fish (forwards).

21. The reaction of a rocket is
an application of the third
law of motion. Various
fuels are burned in the
engine, producing hot
gases.
The hot gases push against
the inside tube of the rocket
and escape out the bottom
of the tube. As the gases
move downward, the rocket
moves in the opposite
direction.

22. When an object moves or tends to move ,
that opposing force which comes into play
is known as friction.

23. Causes of friction:

24. There are three main types of friction:
Static friction: the force of friction which comes
into play when a body is at rest over the surface of
other.
Limiting friction: the maximum value of static
friction which comes into play when body is at the
verge moving.
KineticDynamic friction: the force of friction
which acts on a actually moving body.

25. Slide a book across a
table and watch it
slide to a rest
position. The book
comes to a rest
because of the
presence of a force -
that force being the
force of friction -
which brings the book
to a rest position.

26.  The force of limiting friction between two bodies in contact is
directly proportional to the normal reaction between them i.e.
FαR
 The force of limiting friction is always opposite to the direction in
which an object is at the verge of moving.
 The force of limiting friction is independent of apparent area of
contact as far as the normal reaction between them remains the
same.
 The force of limiting friction depends upon nature of surfaces in
contact and nature of material of surfaces in contact.

28. Coefficient of friction
According to 1st law of limiting friction:
FαR
F= μ R
μ=F/R
Where μ is called coefficient of limiting friction
and is defined as the ratio of limiting friction to
the normal reaction between the two surfaces in
contact.

29. Materials static friction approxiMate
coefficients of
friction
aluMiniuM steel 0.61
copper steel 0.53
Brass steel 0.51
cast iron copper 1.05
cast iron Zinc 0.85
concrete (wet) ruBBer 0.30
concrete (dry) ruBBer 1.00
concrete wood 0.62
copper Glass 0.68
Glass Glass 0.94
polythene steel 0.20
steel steel 0.16
steel ptfe 0.04
ptfe ptfe 0.04
wood wood 0.25–0.5

30. anGle of friction:
 It is defined as the angle which the
resultant of limiting friction and normal
reaction makes with the normal reaction

31. anGle of repose:

32. ϴ=angle of repose

34. advantaGes of friction
 Walking is because of friction
 No two bodies will stick to each
other
 Vehicle’s braking system works
because of friction
 Nuts and bolts would not be able to
hold the machinery together
 Writing would not be possible
 Adhesive will loose their purpose

35. disadvantaGes of friction
 Friction always opposes motion,
therefore extra energy is required to
overcome friction
 Wear and tear of machinery is caused
by friction
 Friction causes production of heat
which damages the machinery