Damped and driven oscillator

We studied the harmonic oscillator which is a system that, when displaced from its equilibrium position, experiences a restoring force, F, proportional to the displacement, x:

If F  is the only force acting on the system, the system is called a simple harmonic oscillator, and it undergoes simple harmonic motion.

If a frictional force (damping) proportional to the velocity is also present, the harmonic oscillator is described as a damped oscillator.

Activity in lab.  Experiment 1                    Experiment2

Depending on the friction coefficient, the system can:

  • Oscillate with a frequency lower than in the undamped case, and an amplitude decreasing with time (underdamped oscillator).
  • Decay to the equilibrium position, without oscillations (overdamped oscillator).

You can lear more about damped oscillator

If an external time dependent force is present, the harmonic oscillator is described as a driven oscillator.


Coupled oscillators


If an object is being forced to vibrate at its natural frequency, resonance will occur and you will observe large amplitude vibrations.

So now can you answer the question : Why do some buildings fall in earthquakes?