# Friction Notes - PowerPoint

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```					Friction
Study Pack #13
Friction
Friction is the force that one surface
exerts on another when the two rub
against each other
The Nature of Friction
Friction acts in a direction opposite to
the object’s direction of motion
Without friction an object would remain
in motion at constant speed! Friction
opposes motion!
The Nature of Friction
The strength of the force of friction
depends on two factors:
   The types of surfaces involved
   How hard the surfaces push together
Is friction useful or not?
Friction can be useful
   It allows us to start and stop moving as well as
change direction
   You are able to walk because there is friction
between your shoes and the floor
   A car moves because of the friction between its
   Thanks to friction you can light a match
   Its so useful you might sometimes want to
increase it!
 Snow shoes
 Ballet dancers
Controlling Friction
There are different kinds of friction
Sliding friction – when solid surfaces
slide over each other
Rolling friction – when an object rolls
over a surface
Fluid friction – the friction that occurs
when an object moves through a liquid
or a gas
Controlling Friction
You must be able to overcome the force
of friction to move
   The force of sliding friction is the most
difficult to overcome, so we change it!