Download What is a force?

Today’s Agenda…
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Bellringer: What does a flat line
represent on a graph of motion?
Graphing Motion WS
Notes on Forces
Homework
Review
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How do we know when an object is in
motion?
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When its distance from another object is
changing
Review
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What do we use to measure motion?
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Speed
Velocity
Acceleration
Today’s Goals…
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I can describe how forces affect motion.
I can explain the difference between
balanced and unbalanced forces.
Activity!
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Take everything off of your desk
Using the materials at your table, you
and your partner are going to
investigate and create different
methods for moving the block across
the table
What did you learn
from the activity?
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What was required to make the block
move?
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A push or a pull
Did the block move when there was no
push or pull?
When you pushed or pulled the block it
was set in motion!
What is a force?
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A force is a push or a pull
When one object pushes or pulls another
object you can say that the first object is
exerting a force on the second object!
For example:
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You exerted a force on the blocks when you made
them move
You exert a force on your pencil when you write
You exert a force on a rock when you throw it
What is a force?
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Forces can be described by how strong
they are AND in what direction
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When you pushed the book you exerted a
force in a different direction than when you
pulled the book!
Some of the forces you exerted on the
books may have been stronger than
others!
What is a force?
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Forces are measured with a spring scale
The units for forces are newtons (N)
Unbalanced Forces
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Imagine that you need to push a heavy
desk across the floor
When you push on the desk you are
exerting a force
If a friend helps you, then the total
force exerted on the desk is your force
plus your friend’s force!
Unbalanced Forces
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When two forces act in the same
direction you add them together
=
Unbalanced Forces
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When two forces act in opposite
directions they combine by subtraction
If one force is greater than the other,
then the overall force is in the direction
of the greater force
=
Unbalanced Forces
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The overall force is sometimes called
the net force
When there is a net force acting on an
object, then the forces are said to be
unbalanced
Unbalanced forces acting on an object
will change an object’s motion
Balanced Forces
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Forces exerted on an object do not
always change an object’s motion or
cause it to move
balanced forces are equal forces acting
on an object in opposite directions
Balanced Forces
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One force is exactly balanced by the other
Balanced forces acting on an object will not
change the object’s motion
When you add equal forces exerted in
opposite directions the net force =
=
0
Revisiting today’s goals…
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I can describe how forces affect motion.
I can explain the difference between
balanced and unbalanced forces.
Assignment!
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Choose an activity (it could be a sport
or a hobby) and describe all the forces
in it that can cause motion.