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Friction

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					Friction
(Stop moving!!)
Friction is a force that opposes
              motion.


                 Many kinds of
                   friction exist.
Amount of friction depends
      on 2 things:

    1. Type of surface

    2. Amount of force
              Surface Matters!
 Friction depends on both of the
   surfaces in contact.




   Just read: (When the hockey puck slides on ice,
      a thin layer of water between the rubber
     and the ice allows the puck to slide easily.)
     More force = More friction

 The greater the
  force squeezing two
  surfaces together,
  the greater the
  friction force.
         Types of friction forces

 Friction is a force,
   measured in
   newtons just like
   any other force.

 Static friction keeps
   an object at rest
   from moving.
 Sliding friction is a
   force that resists
   the motion of an
   object moving
   across a surface.
Other types
 of friction
         Useful friction – just read!
   Friction is also
    important to anyone
    driving a car.
   Grooved tire treads
    allow space for water
    to be channeled away
    from the road-tire
    contact point, allowing
    for more friction in wet
    conditions.
          Useful friction cont.
          (Just keep reading)
                  Shoes are designed
                     to increase the
                     friction between
                     their soles and the
                     ground.
Why do you think these shoes increase friction?

 Players wearing cleats can apply
  greater force against the ground to help
  them move and to keep from slipping.
        Not so useful friction…
 Can you think of examples where friction
  is not so helpful?
 When you…..
     Skin you knee falling 
     Hit a rock on your skateboard and fall 
     Trip and fall 
     Run into a glass door… and fall 
     Trying to run over ice….. And fall 

				
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posted:6/9/2012
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