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Integrated Science
Unit 1, Chapter 3
Unit One: Forces and Motion
Chapter 3 Forces and Motion
3.1
Force, Mass and Acceleration
3.2
Weight, Gravity and Friction
3.3
Equilibrium, Action and Reaction
Chapter 3 Learning Goals
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Explain the meaning of force.
Show how force is required to change the motion of an object.
Use a graph to identify the relationships between variables.
Explain and discuss Newton's second law and the relationship
between force, mass and acceleration.
Describe how changing the mass of the ca affects its
acceleration.
Draw conclusions from experimental data.
Demonstrate qualitatively how friction can affect motion.
Explain Newton's third law of motion.
Identify action-reaction pairs of forces.
Recognize how Newton's third law of motion explains the physics
behind many common activities and useful objects.
Chapter 3 Vocabulary Terms

air friction
 equilibrium
 force
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
friction
 gravity
 inertia
 law of conservation
of momentum
 mass

momentum
newton
 Newton's 1st law of motion
 Newton's 2nd law of motion
Newton's 3rd law of motion
 pounds
 rolling friction
 sliding friction

viscous friction
 weight
3.1 Force, Mass and Acceleration
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Unless you apply force, things
tend to keep on doing what
they were doing in the first
place.
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Force causes an object to
accelerate, while the object’s
mass resists acceleration.
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For every action, there is an
equal and opposite reaction.
3.1 Newton's Second Law
acceleration (m/sec2)
a=F
m
force (newtons, N)
mass (kg)
3.1 Force, Mass, and Acceleration
Key Question:
What is the relationship between force, mass
and acceleration?
*Read text section 3.1
BEFORE Investigation 3.1
3.2 Gravity

What is gravity?
— Gravity is a force.
— Gravity depends on mass.
— Gravity accelerates objects.
3.2 Gravity
 If
you were on Mars, your
force/mass balance would
have to be adjusted.
 The
planet is smaller than
Earth and therefore Mars’s
gravity is weaker.
3.2 Weight
Weight force (N)
Fw = mg
gravity (9.8 m/sec2)
mass (kg)
3.2 Weight and Galileo
 A legend
has it that,
around 1587, Galileo
dropped two balls from
the Leaning Tower of
Pisa to see which would
fall faster.
3.2 Gravity
 The
attractive force
from gravity between
objects of ordinary
mass is incredibly
small.
3.2 Gravity
 You
feel weight
because the mass of
Earth is large enough
to create significant
gravity forces.
3.2 Newton's Law of Universal
Gravitation
 The
force of attraction between two objects is
directly related to the masses of the objects
and inversely related to the square of the
distance between them.
3.2 Newton's Law of Universal
Gravitation
gravity (9.8 m/sec2)
mass 1 (kg)
Force (N)
F = G m1m2
R2
mass 2 (kg)
distance (m)
between m1 and m2
3.2 Weight, Gravity and Friction
Key Question:
How does increasing the mass of the car
affect its acceleration?
*Read text section 3.2
BEFORE Investigation 3.2
3.2 Friction
 Friction
is a force that always opposes motion.
 What
is left is
often called the
net force.
 What
is the net
force acting on
the car?
3.3 Equilibrium, Action and Reaction
Key Question:
What is Newton's third law of motion?
*Read text section 3.3
AFTER Investigation 3.3
3.3 Equilibrium, Action and Reaction

Momentum
—
explains why the speed and the direction of
motion are related to the mass of the object
3.3 Momentum
Momentum (kg-m/sec)
P = mv
velocity (m/sec)
mass (kg)