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FORCES
“ A force to be reckoned with”
EQ: How do balanced and
unbalanced forces affect an
object?
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S8P5.a – Recognize that every object exerts
gravitational force on every other object and
that the force exerted depends on how much
mass the objects have and how far apart they
are.
S8P3.b – Demonstrate the effect of balanced
and unbalanced forces on an object in terms of
gravity, inertia, and friction.
AS YOU ENTER…
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Look around the room and think about
the objects you see in terms of FORCE.
HINT: A force is always exerted by one
object to another object.
Answer the following:
Where do you see a force happening in
this room right now? Which object is
exerting the forces, and which is
receiving it?
Carousel Brainstorming
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Each group should stand in front of one question
station
Using your marker, your group should respond
to the question on the paper for 2-3 minutes.
When time is called rotate clockwise to the next
station and repeat until you have visited all
stations.
Definition of FORCE
A push or pull
 EX:
- Using your fingers to pull open books
- Pushing buttons on a computer keyboard
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FORCE
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All forces have both size and direction.
The unit of force is the Newton (N).
Name two other concepts we are
currently studying that have both size
and direction:
Velocity
Acceleration
DEFINITION OF NET FORCE
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The combination all of the forces acting
on an object.
Determining the Net Force of
an object
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When forces act in the
same direction, you add
the forces to determine
the net force. The net
force will be in the same
direction as the
individual forces.
Determining the Net Force of
an object
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When two forces act in
opposite directions, you
subtract the smaller
force from the larger
force to determine the net
force. The net force will
be in the same direction
as the larger force.
Balanced Forces
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When the sum of the forces acting on any
object equal to zero, the forces are said to be
balanced.
Forces are balanced when they are equal in
size and opposite in direction.
THERE IS NO CHANGE IN VELOCITY WHEN
THE FORCES ARE BALANCED! Constant
speed exists.
Examples of Balanced Forces
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A
A
A
A
light hanging from the ceiling
Bird’s nest in a tree
hat resting on your head
resting elevator
How is this picture an
Example of Balanced Forces?
Unbalanced Forces
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Unbalanced forces occur when the sum of the
forces acting on any object is not equal to
zero.
Unbalanced forces produce a change in motion,
such as a change in speed or a change in
direction.
Unbalanced forces are necessary to cause a
nonmoving object to start moving.
Examples of Unbalanced
Forces
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Soccer players kicking a soccer ball.
-Competing in an arm wrestling
competition against a world famous body
builder
Unbalanced Forces

Unbalanced forces occur when the sum
of the forces acting on any object is not
equal to zero. Unbalanced forces
produce a change in motion, such as a
change in speed or a change in direction.
Unbalanced forces are necessary to
cause a nonmoving object to start
moving.
THE BIG IDEA
 Unbalanced
forces cause
changes in motion that can
be predicted and described.
Forces, Mass & Acceleration
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An object accelerates when a net force
acts upon it.
The relationship between force, mass,
and acceleration can be summarized by
the following formula:
F = ma
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Acceleration depends on both the net
force applied and the mass of the
object.
Example Problem #1
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Example Problem #1
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Example Problem #2
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Example Problem #2
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Draw a T chart on the right side of your
paper and complete the instructions in each
box.
How much force is
needed to make a
150 kg object
accelerate at a rate
of 2 m/s2?
Draw a Visual
Representation of
Unbalanced Force
Write an Example
of a
alsd
Balanced Force.
Where do you see a
force happening in this
room right now? Which
object is exerting the
forces, and which is
receiving it?