1. FORCE
This is HEAVY!
I can’t hold it
anymore!
Can someone help
me?

2. FORCE
• push or pull
• object’s interaction with its
environment
• vector quantity
• unit is Newton

3. NET FORCE
• the sum of all the forces acting on
the object.
• a physical quantity that is capable of
changing an object’s state of motion
5 N3 N 3 N
5 N
Net force = 2N, right Net force = 8N, right

4. Four Fundamental Forces
1. Gravitational Force
– Force of attraction between two masses
Position of the stars and
planets
2
21
r
mm
GFg

5. 2. Electromagnetic Force
Force that affects charge particles
Your hair will be attracted to
a charged balloon
The electrons from the
clouds will travel towards
the land - thunderbolts

6. 3. Weak Nuclear Force
4. Strong Nuclear Force
Four Fundamental Forces
Radioactive decay
Binds proton in the
nucleus

7. Forces acted on an object
1. Weight
- gravitational attraction of an
object and the earth
- always directed downwards
- W = mg
weight
Normal
force
2. Normal Force
- support force exerted upon
an object
- perpendicular to surface

8. Forces acted on an object
3. Applied force
- force applied simply by
pushing or pulling
weight
Normal
force
Applied
force
Friction
4. Friction
- force exerted by a surface as
an object moves across it
- parallel to surface and
opposite to the direction of
motion

9. Forces acted on an object
5. Tension
- force which is transmitted through
a string, rope, cable or wire when it
is pulled tight by forces acting from
opposite ends.
T
e
n
s
i
o
n
6. Air resistance
- force exerted by the air as an
object moves in it
- opposite to the direction of
motion

10. Newton’s
Law of Motion
1. Law of inertia
2. Law of
Acceleration
3. Law of Interaction

11. I have answer to
your inquiry 

12. Law of Inertia
The body at rest tends to remain at rest,
and a body in motion continues to move
at constant velocity unless acted upon
by a net force.
Inertia is the property of a body which
resists any change in its state of rest or
motion.
Inertia is proportional to mass.

13. Importance of using Seatbelts

14. Importance of Seatbelts
Seatbelt exerts force on
the person for him not
to move forward when
it suddenly stops.
Force
(seatbelt)

15. Try This at Home
Egg Drop Challenge

16. Law of
Acceleration
The acceleration of an
object depends directly
upon the net force acting
upon the object, and
inversely upon the mass of
the object.

17. Law of Acceleration
Acceleration is directly proportional to mass
Acceleration is directly proportional to mass
a F
a 1/m
a = F/m

18. Law of Acceleration
maFor
m
F
a
Force (N) Mass (kg) Acceleration (m/s2
) Your answer is...
20 ? 2 Try again
15 3 ? Try again
? 0.9 3 Try again
30 ? 0.5 Try again
0.6 0.2 ? Try again
? 20 10 Try again

19. Law of
Interaction
For every action,
there is an equal and
opposite reaction.

20. Law of Interaction
You push
the wall
by 50 N
The wall
push you
by 50 N in
the
opposite
direction
Action
Reaction

21. Law of Interaction
Action Reaction
You push the ground
downward
The apple is pulled by
the Earth downward
The rocket exhausts
gas to the ground
downward
The ground will push
you upward
The Earth is pulled by
the apple upward
The gas will push the
rocket upward