Download Force and Motion

Motion and Forces
Section 2-3
What is a force?
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Push or pull one body exerts on another
Push a door
Stretch a rubber band
Shove a book across the table
Some are obvious (car hits tree), others
are not (floor pushing on feet).
Effects of Forces on Objects
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Does the object move when a force is
exerted on it?
Balanced forces: equal in size but
opposite in direction (tug of war)
Unbalanced Forces: (Net forces)
change the velocity (speed or direction)
of the object
Inertia and Mass
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Inertia: A moving object keeps moving
and a stationary object remains
stationary until a force acts on it.
Compare the inertia of bowling ball with
tennis ball
More mass = more inertia
Newton’s first law
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An object in motion remains in motion
unless a net force acts on it. An object
at rest remains at rest unless a net
force acts on it. (INERTIA)
Wheelbarrow with rake on top strikes a
rock. What happens?
Why do cars have seatbelts?
Friction
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Force that opposes motion between two
surfaces that are touching.
Amount of friction depends on: The
kinds of surfaces, and the force
pressing the surfaces together.