Chapter 4
Friction
Definitions
• Mass - The quantity of material in an object.
• Weight - The force due to gravity on an object
• Force - Any influence that can cause an object
to accelerate.
• Friction - the resistive force that opposes the
motion or attempted motion of an object.
Definitions
• Free Fall - Motion under the influence of
gravitational pull only.
• Terminal velocity - the speed at which the
acceleration of a falling object is balanced by
air resistance.
Forces and Acceleration
• F = m*a
• SF is a powerful tool in statics and dynamics.
• Forces that detract from a system are called
non-conservative forces.
Friction
• Occurs when two materials come into contact.
• Friction is the result of imperfections material
surfaces.
• Friction always opposes motion.
SF and Friction
• Friction is always opposite the path of motion.
• The friction force is based on the normal or
support force.
• Static friction is greater then dynamic friction.
Drag
• Fluid friction is called drag.
• Drag is dependant on speed and contact area.
• Drag in air is approximately velocity2.