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Sir Isaac Newton
English physicist &
mathematician
…he developed the
3 laws of motion
Motion is any change in
position!
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p. 45
Forces
a push or a pull
Forces can have the ability
to change motion!!!
Unit: Newton (N)
p. 46
Force
vs.
Amount of matter
(resists forces)
Mass
p. 47
Sir Isaac Newton’s
3 Laws of Motion:
Newton’s 1st Law (Law of Inertia)
“An object in motion wants to
stay in motion, an object at
rest wants to stay at rest.”
FYI- Inertia depends upon
mass.
p. 48
Newton’s 2nd Law
(Law of Acceleration)
“Acceleration occurs in the
direction of the force.”
 the object’s mass…
and also the
size of the force…
determine the object’s
acceleration
p. 49
Newton’s 2nd Law
(calculating acceleration)
Formula: Acceleration
(m/s2)
Force (N)
F/
A= m
Mass (Kg)
Ex.) p. 49, 50
p. 49
Types of Forces
Forces cause motion
Motion depends on net force
Forces can be
balanced or
unbalanced
p. 51
Balanced Forces
Equal in size
Opposite in direction
No motion occurs!
(equilibrium)
Like a tie in an
arm wrestling
match!
p. 51
Unbalanced Forces
Unequal in size
Opposite in direction
2nd law: unbalanced
forces cause acceleration
p. 51
Gravity
A force that pulls
us downward
toward the center
of the Earth.
Gravity pulls everything
down with a force of
9.8 N (Newtons)
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p. 52
The gravitational force felt
by an object is related to its
mass.
Mass does NOT change, but
your weight will change with
a change in gravity (moon)!
Mass
Amount of matter
(resists forces)
vs.
mass x gravity
(force)
Weight
p. 53
Calculating Weight
Formula: Weight
force (N)
Mass (Kg)
g
m
=
Fw
Gravity (9.8
m/s2)
p. 53
Friction
opposes an object’s motion
Four Types of Friction:
1. Air friction
2. Viscous friction
3. Sliding friction
4. Rolling friction
p. 54
1. Air Friction
Also called Air resistance
(aerodynamics reduce
the air friction)
Ex) falling objects or airplanes
p. 54
2. Viscous Friction
Moving through
a liquid, or fluid
Ex) swimming
p. 54
3. Sliding Friction
Two surfaces rub
against one another
Ex) rubbing hands or
clapping
Caused by irregularities in
the surface
p. 54
4. Rolling Friction
An object rolls over a surface
Ex) ball bearings, roller skates, or
wheels
Figure 3.9
p. 54
Newton’s 3rd Law
(Action /Reaction)
“For every action,
there is an equal and
opposite reaction.”
p. 57
Calculating Momentum
Formula:
Momentum
(Kg-m/s)
Mass (Kg)
P= m v
Velocity
(m/s)
p. 58
Law of Conservation of Momentum
Total amount of momentum
can not change
ex.) p. 59
p. 58