Newton's laws of motion are three physical laws that, together, laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces.

1. NEWTON'S LAW OF
MOTION
Prepared by: Joryn Cinco Ramo

2. NEWTON’S FIRST LAW OF MOTION

3. • Newton’s first law of motion describes how an object at
rest will stay at rest. It also describes how moving object
at constant velocity stays in motion. In both cases, force
influences an object’s motion. What characteristics of an
object makes it harder to stop?

4. • The first law of motion is the law of inertia. It states that:
• An object at rest stays at rest, and an object in
stays in motion at constant velocity unless acted
by a net external force.

5. • Inertia is the tendency of an object to resist motion. For objects at rest, inertia depends on
mass. The larger the object, the larger is the inertia.
• For moving objects, inertia depends on the object’s momentum. The greater the
of an object, the harder it is to stop from moving.

6. EXAMPLE
• Let us consider a pool ball set on the table. Before a strike from another
ball or the cue stick, the pool balls are at rest. It will remain at rest as long
as no external force will act on it. When the cue ball has been struck, the
cue ball will continue to move with constant velocity as long as no
external force acts on it.

12. NEWTON'S SECOND LAW OF
MOTION
• If you are asked to push a 1kg box and a boulder, it will be easier for you to move
a 1kg box compared to the boulder at the same distance. Moving the boulder will
require greater amount of force compared to moving a 1kg box.
• How is mass, force, and the acceleration of an object related to each other?

13. LEARN ABOUT IT!
• The second law of motion is the law of acceleration. It
states that:
• The acceleration is produced when a net force acts on
mass, and that acceleration is directly proportional to
the force acting on the object and inversely proportional
to the object's mass.

14. •Newton's second law could be
mathematically written as
•F=ma
•where a is the acceleration in (m/s2), F is
the force in newton (N), m is the mass
in kilograms (kg).
•The equation is also commonly written as
•F=ma.

16. EXAMPLE 1
•How much force is needed to accelerate a 75 kg
object at a rate of 5 m/s2?

17. EXAMPLE 2
•How much force is needed to accelerate a 60 kg
object at a rate of 2.5 m/s2?

18. EXAMPLE 3
•Chris wanted to move a 5 kg box across the hall. To
do this, he applied 50 N of force. What is the
acceleration of the box?

19. EXAMPLE 4
•A physics book with a mass of 1.5 kg was moved
across a table by a 45 N force. What is the
acceleration of the book?

20. EXAMPLE 5
•A 6.125 N force caused a ball to accelerate at 9.8
m/s2. What is the mass of the ball in grams?

21. EXAMPLE 6
•A 4800 N force acts on a car at rest and causes it to
accelerate at 2.4m/s2.What is the mass of the car in
grams

22. FORCE AND ACCELERATION
• The first part of the second law tells that the greater the
unbalanced force, the greater the acceleration of the body being
acted upon. If the force F1 is applied to a body at one time and a
force F2 at another time, then
• F1/a1=F2/a2

23. EXAMPLE 7
•A force of 5.0 N accelerates an object by 2.0 m/s2.
what force is needed to give the same object an
acceleration of 3.4 m/s2.

24. EXAMPLE 8
•Two forces of magnitudes 6.0 N and 4.0 N act on a
3.2 kg body. What is the acceleration produced
when these forces are acting in the same direction?
What is the acceleration produced when these
forces are oppositely directed?

25. IMPULSE-MOMENTUM THEOREM

26. MOMENTUM
• is a quantity that describes an object's resistance to
stopping (a kind of "moving inertia").
• is represented by the symbol p (boldface).
• is the product of an object's mass and velocity.
• p = mv
• is a vector quantity (since velocity is a vector and mass
is a scalar).

27. IMPULSE
•is a quantity that describes the effect of a net force
acting on an object (a kind of "moving force").
•is represented by the symbol J (boldface).
•is the product of the average net force acting on an
object and its duration.
•J=Ft

28. RECALL
• a=vf-vi/t
• Substituting in the equation F=ma
• Ft-mvi-mvf
• This equation tells us that a net force F acts on the
body, the impulse of the net force is equal to the
change in momentum of the body. The statement is
called the impulse-momentum theorem, which is
considered as an alternative statement of Newton’s
second law of motion.

29. EXAMPLE 9
• An air bag increases impact time to reduce the force
experienced by a driver of a car during collision. A bus hit
a car, which is parked on the road, from behind. The car
accelerates to 4.5 m/s in 0.15s. a.) What force does the
driver of the car experience is he is not wearing a seat
belt during the accident? Assume that the combined
mass of the car and driver is 2580 kg. b. If the car has an
air bag and crumple zones increase the impact time t 0.45
s, what force is experienced by the driver?

30. NEWTON'S THIRD LAW OF
MOTION
• Newton’s third law of motion explains how objects interact with each
other in terms of forces. The third law of motion is also called the law of
interaction. It states that:
• For every action, there is an equal and opposite reaction.
• When a force acts on an object, another force reacts. The two forces
that act and reacts are called action-and-reaction forces. The three
characteristics of an action-and-reaction force are:
1. equal in magnitude,
2. opposite in direction, and
3. acting on different objects.

31. EXAMPLE
• The action force is the force on the table due to the weight of the book. In return,
the table reacts by applying a force in the book that is equal in magnitude but
opposite in direction.

35. REFERENCE
• Quipper Philippines