Download What is a Force?

What is a Force?
“May the force be with you.”
S8P3: Students will investigate the
relationship between force, mass, and the
motion of objects.
a. Determine the relationship between
velocity and acceleration.
b. Demonstrate the effect of balanced and
unbalanced forces on an object in terms of
gravity, inertia, and friction.
What Is A Force?
Forces Act On
Objects
Forces in
Combination
Unbalanced
and Balanced
Forces
•
1.
2.
3.
4.
Demonstrate the effect of balanced and
unbalanced forces on an object in terms
of gravity, inertia, and friction.
What is a force?
What is a net force?
Examples of forces in the same direction.
(including illustration)
Examples of forces in the opposite
direction (including illustration).
5. Define unbalanced force and know what
it produces.
• Give at 2 examples of objects with
unbalanced forces.
• Define balanced force and know what it
produces.
• Give at 2 examples of objects with
balanced forces.
• We often use the word “force” in everyday
conversation:
• “The storm had a lot of force.”
• “Our softball and football teams are forces
to be reckoned with.”
• “A flat tire forced me to stop riding my
bicycle.”
• “The inning ended with a force-out at
second base.”
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•
•
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In science, a force is a push or pull.
All forces have size and direction.
Forces are everywhere.
Anytime you see something moving, you
can be sure that it was a force that its
motion was created by a force.
• Scientists express force using a unit called
the newton (N).
• The more newtons, the more force.
Forces Act on Objects
• All forces are exerted by one object on
another object.
• For any push to occur, something has to
receive the push.
• You can’t push nothing.
• The same is true of a pull.
Why doesn’t the force exerted on
the chair by the man cause it to
move?
The earth is also
exerting a force on
the chair. The man
is pushing down on
the chair and the
earth is pushing up
on the chair.
• It is not always easy to tell what is exerting
a force or receiving a force.
• You cannot see the force that pulls
magnets to refrigerator.
Forces in Combination
• Often more than one force is exerted on
an object at the same time.
• The net force is the force that results from
combining all the forces exerted on an
object.
How is net force determined?
• Forces in the Same Direction
When the forces are in the same direction,
you add the forces together to determine
the net force.
One of the men is
pushing on one end
of the piano, and
the other man is
pulling on the other
end.
Forces in Different Directions
When the forces are in different directions,
you subtract the smaller force from the
larger to determine the net force.
The larger
dog is
exerting the
greater force.
Unbalanced and Balanced Forces
• Unbalanced forces produce a change in
motion.
• When the net force on an object is not 0,
the forces on the object are unbalanced.
• Unbalanced forces produce a change in
motion (acceleration).
• Unbalanced forces are necessary to cause
a nonmoving object to start moving.
• Unbalanced forces are also necessary to
change to motion of moving objects.
The soccer ball
received an
unbalanced force
and moves in a new
direction with a new
speed.
Balanced Forces Produce No
Change In Motion
• When the forces applied to an object produce a
net force of zero, the forces are balanced.
• Balanced forces do not cause a nonmoving
object to start moving.
• Balanced forces will not cause a change in the
motion of a moving object.
• acting on them.
• Many object around you have only balanced
forces