CIE A Level Physics (9702) 2019-2021

Revision Notes

19.1.1 Oscillations & Simple Harmonic Motion

Free Oscillations

  • A free oscillation is defined as:

A vibration with no external forces acting on it

  • A free oscillation has constant energy and amplitude ie. no energy loss or gain
  • An example of a free oscillation is a plucked guitar string
    • It will vibrate for some time after it is plucked and released
  • Free oscillators vibrate at a particular frequency
    • This is called the natural frequency of the vibration
  • Every oscillator has a natural frequency of vibration
    • This is the frequency in which it vibrates freely after an initial disturbance

Motion of an Oscillator

  • An experimental and graphical method can be used to observe the motion of a simple mass-spring system
    • Tie a pencil together with the mass and set the mass in free oscillations by displacing it downwards slightly
  • The oscillations will move the pencil up and down
    • On a piece of graph paper, allow the pencil to trace the path of the oscillations by pulling the paper sideways as the mass-spring system oscillates up and down
  • The oscillations will produce a curved, periodic graph
    • This will decrease in amplitude as the mass-spring system slows down

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