FRICTION

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FRICTION
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Quick review of force

• A force is a push or a pull.
• A force is anything that causes an object to
  start moving, stop moving, or change direction.
• Balanced forces do not cause changes in motion.
• The net force is the total of all forces acting
  on an object. If net force is 0 Newtons, THERE IS
  NO CHANGE IN MOTION.

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Friction A force opposing motion

• Imagine sliding down a waterslide with no water.
  OUCH!!
• The reason you would have a burn and be in pain
  is friction.
• Friction is a force that opposes motion between
  two surfaces that are touching.

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What causes friction?

• Friction occurs because the surface of any object
  is rough.
• The smoother the surface, the less friction
  between them.
• Rough surfaces create more friction.
• Think of trying to slide in your socks across
  carpet!

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Types of Friction

• There are two categories of friction kinetic and
  static
• Kinetic friction involves moving objects.
• Static friction involves objects NOT in motion.

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The next slides involve kinetic friction only.
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Sliding Friction

• Sliding friction occurs between two solid objects
  touching.
• Rub your hands together, that is sliding
  friction.
• Sliding friction creates a tremendous amount of
  heat.
• You use sliding friction when you go sledding,
  apply the brakes on a car, or write with a pencil.

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Rolling Friction

• Rolling friction involves wheels or ball
  bearings.
• Rolling friction reduces sliding friction.
• Imagine pushing a car with no wheels!

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Fluid Friction

• Fluid friction involves objects traveling through
  fluids.
• A fluid is a liquid or a gas.
• Some examples include water on a waterslide,
  skydiving, meteorites, and slipping on wet floors.

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Static Friction

• When a force is applied to an object, but the
  object does not move, static friction occurs.
• Static friction keeps you in your seat. It keeps
  objects from sliding around when you dont want
  them to.
• Without static friction, you would not be able to
  walk because your feet would not grip the floor.

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Friction Good or Evil?

• Friction can be very helpful or harmful.
• Without friction, you could not stop a car.
• However, friction between moving objects wears
  them down.

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Wheres the friction? 1
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Wheres the friction? 2
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Wheres the friction? 3