Newton's three laws of motion are: 1) An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. 2) The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the direction of the net force, and inversely proportional to the mass of the object. 3) Whenever one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

1. NEWTON’S LAW
OF MOTION

2. Law of Inertia
• “An object that is at rest will remain at rest
and an object in motion will continue
moving at a constant speed in a straight
line unless acted upon by an external
force.”
• If you are not going to do anything, nothing
will happen

3. • This tendency of a body to peserve its
state of motion is called inertia.
• The inertia of an object depends on its
mass.
• There is zero net force acting on an object
that is at rest or that is moving with a
constant speed in a straight line.

4. Law of Acceleration
• The acceleration of an object is directly
proportional to the net force acting on the
object, is in the direction of the net force
and is inversely proportional to the mass
of the object.
a =
ƩF
m

5. Example:
Neglecting friction, what
constant force will give a
mass of 50kg an
acceleration of 5m/s?

6. Law of Interaction
• “Whenever one object exerts a force on a
second object, the second object exerts an
equal force on the first.”
• To every action, there is always an equal
and opposite reaction.
• Forces always come in pairs.

7. Mass and Weight
• Mass is a measure of an object’s
inertia.
• Weight is a force upon an object
due to gravity.

8. FORCE
• The sum of all forces acting on a body is
called the net force or the resultant force.
• The force that tends to balance or bring an
object into a state of balance is called the
equilibrant force.
• Force are also capable of producing
acceleration, rotation and deformation.

9. Contact and Non-contact Forces
5/17/2023 The NEED Project 9
• Forces are sometimes classified as either
contact or non-contact force.
• Contact forces arise when there is a
physical contact between the interacting
body.
• Non-contact forces are forces that occur
when bodies interact t a distance.

10. Contact Force: Friction
5/17/2023 The NEED Project 10
• Friction is a force between two bodies that
are in contact with each other.
• It naturally opposes the motion of an
object.
• The greater the weight of the object , the
greater the amount of frictional force.
• Rough surfaces have greater frictional force
compared to smooth surfaces.

11. 5/17/2023 The NEED Project 11
F
• Friction can be static or kinetic.
• Static friction resists the initiation of motion.
• Kinetic friction is the resistnce that a moving
object meets as it slides or rolls on a
surface.
Kinetic Friction
Static Friction
= Nμ K
s F
= Nμ = Nμ
s K

12. 5/17/2023 The NEED Project 12
• Refers to the force apllied to an object
through a cable, string, ropes, chains and
etc.
Contact Force: Tension

13. 5/17/2023 The NEED Project 13
• Gravitational force is an interaction of two
bodies primarily because of its mass.
• The weight of an object changes but the
mass of the object remains constant.
Non - Contact Force: Gravitational Force

14. 5/17/2023 The NEED Project 14
• This is a force between interacting charges.
• Like charges repel each other while unlike
charges attract.
Non - Contact Force: Electrical Force

15. 5/17/2023 The NEED Project 15
• This is a force between interacting magnets
or between materials with high magnetic
properties.
• Like poles of a magnet repel each other
while unlike poles of a magnet attract.
Non - Contact Force: Magnetic Force