Oscillations and Waves

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Oscillations and Waves

• Forced Oscillations and Resonance

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• Damping
• - Caused by resistive forces that always oppose
  motion e.g. friction
• Energy is dissipated by these forces. E.g.
  friction or magnetic damping can result in
  kinetic energy being dissipated as heat energy
  flows from the system.
• Damped systems do not describe SHM.

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• Degrees of damping
• under damped this means the body will oscillate
  before coming to rest at the equilibrium
  position.

• critically damped the body will come to rest at
  the equilibrium position in the shortest possible
  time, without oscillating.
• - over damped this means the body will take
  longer to come to rest

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• Resonance
• Natural frequency the frequency at which a body
  will freely oscillate at if plucked or banged or
  otherwise set in motion.
• Forced oscillations these occur when a driver
  oscillating body causes another body (the
  driven body) to oscillate at the same frequency
  (not necessarily its natural frequency).
• Resonance This occurs when the forced vibration
  frequency of the driver is equal to a driven
  objects natural frequency.

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Resonance of a text book
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Resonance of a mass on a spring
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• E.g. The Tacoma narrows suspension bridge
• Video clip
• E.g. Breaking a wine glass using resonance
• You tube clip

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