A brief introduction to force and motion

1. Unit 1
Motion
Lesson 1
The nature of force

2. FORCE AND MOTION
Balanced and Unbalanced Forces
Velocity and Acceleration

4. Motion
• What is motion?
• A change in the position of an object
over time.

5. Overview
• Galileo was successful in providing an
experimental and theoretical background on
how to describe motion.
• Newton who answered and explained why
objects move and why they accelerate.
• Newton’s Laws of Motion

6. • What causes an object to move?
- A force
• What is force?
- Is define as a push or pull acting upon
an object.

7. Example:
1. A game of tug-of-war wherein
two opposing teams are pulling on the
ropes.
2. Pushing a cart at the
supermarket.

8. Aside from seeing force as simple push
and pull, force can be viewed as any
influence capable of producing a change
in the state of motion.
• How do you know if something is in
motion or has moved?
• What changes can force do to motion?

9. 1. Force can make an object moved
starting from rest position.
2. Force can make a moving object
stop.
3. Force can change the direction of a
moving object.

10. ➢ Whenever an object moves from a
rest position, its velocity increases.
➢ If it stops, then its velocity
decreases.
➢ When it changes direction the velocity
also changes.

11. ➢ A change in the state of motion means
change in velocity.
➢ Whenever velocity changes with
respect to time, acceleration
produced.
➢ A change in state of motion means a
change in velocity or simply the
occurrence of acceleration.

12. ➢ Velocity, acceleration, and force are
vector quantities.
➢ It must have magnitude and
direction.
➢ Force is a quantity which is measured
using a standard metric unit known as
“ newton (N)”.

13. ➢ 1 newton is the amount of force
required to give 1-kg mass an
acceleration of 1 m/s².
➢ 1N = 1 kg m/s²

14. ➢ A force may not always cause an
object to move, especially if there is
more than one force.
• What will happen if there is a
presence of another force?

15. ➢ The presence of another force may
cancel the effect of the other force;
causing no change in the state of
motion of an object.
➢ If a single force is present, it can
cause a change in the state of
motion.

16. ➢ Single force that acts and causes a
change in the state of motion of an
object is known as the net force or
the resultant force.
➢ The resultant force is the vector sum
of all the forces acting on an object.

17. ➢ Several forces can be combined or
added to produce a single force- net
force.
➢ A net force of zero indicates that all
the forces cancel each other’s
effect.

18. + =
1
2
3
+ =
=
+ 0
2 forces can
combine so they
add
together(1), or
subtract from
each other (2).
They may also
cancel each
other(3).

19. ➢ If no changes in the state of motion
is produced, these forces are said to
be BALANCED FORCE.
➢ If there is a net force, then this
force is said to be the UNBALANCED
FORCE.

20. Types of Forces
➢ Forces can be classified into two basic
types based on how they are applied or
how they act on the other objects.
• Contact forces
• Non-contact forces or action-at-a
distance force.

21. Contact Forces
1. Applied Force 𝐹𝑎𝑝𝑝
- force applied to an object by
another object or person.
- the direction of the force applied
depends on how the force is applied.

22. 2. Normal Force (N)
- support force exerted upon an
object that is in contact with another
object.
- referred as pressing force.
- always directed toward the
pressing object and acts perpendicularly
to the surface of the object.

23. 3. Frictional Force (f)
- force exerted by the surfaces in
contact with each other and move
relatively being pressed with each other.
- friction opposed the motion.

24. - results when two surfaces are
pressed together closely, causing
attractive intermolecular forces bet. The
molecules of the 2 diff. surfaces.
-can be calculated using equation :
f=μN, where μ is the coefficient of
friction and N is the normal force.

25. 4. Air Resistance Force (Fair)
- is a special type of frictional force
that acts on objects as they travel
through the air.
- always opposes the motion of the
moving object.
- it is most noticeable in objects that
travel at high speed or in objects with
large surface areas.

27. 5. Tensional Force (T)
- is the force which is transmitted
through a string, rope, or wire when it is
pulled tight by forces acting at each end.

28. 6. Spring Force (𝐹𝑠𝑝𝑟𝑖𝑛𝑔)
- force exerted by a compressed or
stretched spring on any object that is
attached to the spring.

29. Non- Contact Forces
1. Force of Gravity (also Known as Weight,
W)
- force with which the Earth, moon, or
massive body attracts an object toward
itself.

30. - this is the weight of an object.
- force on an object on Earth is always
equal to the weight of the object as given
by the equation W=Mg, where g is the
acceleration and due to gravity which has a
value of 9.8 m/s²( on Earth) and m is the
object’s mass (in kg) .

31. 2. Electrical Force
- this is the force that exist
between charges. It can either be
attractive or repulsive force.
3. Magnetic Force
- this is the force that exist in
magnets. It is the force that makes
magnets attract or repel objects or other
magnets.

32. Free-Body Diagram FBD
- forces can be seen based on how they
act on an object.
- forces acting on an object can be
shown by representing them as arrows.
- this representation is called a Free-
Body Diagram (FBD).

33. When constructing FBD’s, the following
assumptions are made:
1. Pulleys are assumed frictionless;
2. Pulleys are assumed weightless;
3. Ropes, cables, cords, and wires are
assumed weightless.

34. In constructing FBD, one frees the body (or
object) from its environment and draws the
body indicating the magnitudes and
direction of all forces acting on the body.