This document discusses Newton's first law of motion and related concepts like force, inertia, and frames of reference. It defines force as a push or pull between objects and explains that forces can be contact forces requiring physical touch or non-contact forces acting over a distance. Newton's first law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and direction unless acted upon by an unbalanced force. It also introduces the concept of inertia and differentiates between mass and weight.

1. Force and
Newton's First
Law of Motion

2. OBJECTIVES
At the end of this lesson, you will be able to:
• differentiate contact and non-contact forces;
• apply Newton’s 1st law to obtain quantitative and
qualitative conclusions about the contact and non-
contact forces acting on a body in equilibrium;
• define inertial frames of reference; and
• distinguish mass and weight.
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3. 3
WHY DOES IT MOVE?
“FORCE”

4. WHAT IS A FORCE?
• is a push or pull of an object.
• It is an interaction between two
objects or between an object and
its environment.
• Force is a vector quantity, it has magnitude and
direction. In most cases, it is denoted by the
variable F.

5. WHAT IS THE UNIT OF FORCE?
• Force is a quantity that is measured using the
standard metric unit known as the Newton.
• A Newton is denoted by the variable N and is
equivalent to the product of a unit mass multiplied by
a unit acceleration as shown:

6. FORCE SCALAR OR VECTOR?
• force is a vector quantity. Therefore, a force has a
magnitude and direction.
• For forces which are directed towards the primary
directions, their sign convention is:
+ positive when directed upwards or to the right.
- negative when directed downwards or to the left.

7. FORCE SCALAR OR VECTOR?
• forces with their magnitude and
direction can also graphically as shown
below:

8. NET FORCE OR RESULTANT FORCE
8
• is the sum of all the forces that act on
the system
Free body diagram

9. BALANCED VS UNBALANCED FORCES
• Balanced Forces forces acting on an object that do not cause change
in the object's motions. (net force=0)
•
Unbalanced forces forces that cause a change in an object's motion

10. CONTACT AND NON-CONTACT FORCE
• Contact Force - these are forces that involve physical
contact between bodies
• Non-contact Force or Action-at-a-distance Force - these
are forces that do not involve physical contact between
bodies

11. CONTACT AND NON-CONTACT FORCE
Contact Force Non-contact Force
Applied Force
Gravitational Force
(Weight)
Normal Force Electrical Force
Friction Force Magnetic Force
Tension Force
Spring Force
Air/Fluid Resistance
Force

12. Applied Force (Fapp)
Applied force is the force applied to an object by a person or
another object.

13. Normal Force (FN or N)
The normal force is the support force or reaction force exerted
upon an object that is in contact with another stable object.
The normal force is always perpendicular to the surface.

14. Friction Force (Ff)
Friction occurs when a surface resists the sliding of an object.
It is always parallel to the surface and directed opposite of the
motion.

15. Tension Force (Ft or T)
Tension is a pulling force exerted on an object by a
rope, string, cord, or chain. It is always a pull and
never a push kind of force.

16. Air/Fluid Resistance Force (Fair/fluid)
The air/fluid resistance is a special type of frictional force that
acts upon objects as they travel through the air. This air
resistance is sometimes called drag force and fluid resistance
is sometimes called buoyant force.

17. Gravitational Force or Weight (Fgrav or W)
The pull of gravity on an object and is also called weight. It is the force of
gravity with which the earth, moon, or other massively large object
attracts another object towards itself. Since the earth is round and the
center is inside it, the direction of the weight is always downward.

18. Magnetic Force (Fmag)
The magnetic force is the attraction or repulsion that
arises between electrically charged particles because
of their motion. Magnetism is closely related to
electricity.

19. ISAAC NEWTON’S LAW OF MOTION
Sir Isaac Newton was a physicist
and mathematician who
developed the principles of
modern physics, including the
laws of motion and is credited as
one of the great minds of the
17th-century Scientific
Revolution.

20. ISAAC NEWTON’S LAW OF MOTION
LAW #1: A body at rest will remain at rest, and a
body in motion will remain in motion unless it is
acted upon by an external force.
LAW #2: The force acting on an object is equal to
the mass of that object times its acceleration,
F=ma
LAW #3: For every action, there is an equal and
opposite reaction.

21. 1ST LAW OF MOTION
"A body at rest will remain at rest, and a
body in motion will remain in motion,
unless it is acted upon by an external
force."

22. 1ST LAW OF MOTION (Law of Inertia)
Inertia is the resistance an object has to a change in its
state of motion.
“The more inertia that an object has, the more mass that it has”

23. 1ST LAW OF MOTION (Law of Inertia)
There are three types of Inertia
following Newton's 1st Law:
1. Inertia of Rest
2. Inertia of Motion
3.Inertia of Direction

24. 1ST LAW OF MOTION (Law of Inertia)
There are three types of Inertia
following Newton's 1st Law:
1. Inertia of Rest
2. Inertia of Motion
3.Inertia of Direction

25. 1ST LAW OF MOTION (Law of Inertia)
There are three types of Inertia
following Newton's 1st Law:
1. Inertia of Rest
2. Inertia of Motion
3.Inertia of Direction

26. INERTIAL REFERENCE FRAME
Inertial frame of reference is any frame in which an object remains
either at rest or at a constant velocity unless another force acts
upon it.

27. WEIGHT
NOTE: g may varies on the location of the problem.
acceleration due to the gravity of the EARTH is 9.8m/s2 or 32ft/s2
and the acceleration due to the gravity of the MOON is 1.6m/s2 or 5.3ft/s2

28. EXAMPLE 1
What is Ivan's weight if he weighs
55 kg?
If Ivan goes to the Moon (gmoon=1.6m/s2), what will be
his new weight?