FRICTION!

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FRICTION!
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• Friction force that opposes (slows) motion
• Vector Quantity
• Types of Friction Rolling, Sliding and Fluid
• Frictional Force Depends on
• Normal Force of object (Weight)
• Type of surface

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• Static Friction Opposes the START of motion
  (when object is at rest)
• Kinetic Friction Objects in contact that are
  moving past each other.
• Kinetic Friction lt Static Friction

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• Frictional forces are PARALLEL to surfaces
• In order to get an object moving or keep it
  moving, it must overcome the frictional force.

Fapplied 14.8 N
Ffs 14.8 N
20 N Steel Box
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• If Frictional Force Applied Force
• then the object is at rest or moving at constant
  velocity
• If Applied Force gt Frictional Force
• then the object is accelerating in the direction
  of the applied force.

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Force of Friction
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Problem

• A force of 10 Newtons towards the right is
  exerted on a wooden crate initially moving to the
  right on a horizontal wooden floor. The crate
  weighs 25 Newtons.
• Calculate the magnitude of the force of friction
  between the crate and the floor.
• What is the net force acting on the crate?
• Is the crate accelerating?