Damped and forced oscillations Flashcards
Understand free and forced oscillations, damped oscillations, resonance, resonance problems and damping solutions,
Give an example of a free oscillation.
Letting a pendulum swing freely, preferably in a vacuum.
The situation is set up for a continuous exchange of potential and kinetic energy, caused by a restoring force which is proportional to the displacement.
What is a natural frequency?
The frequency at which any oscillating system naturally oscillates at when left alone.
What is a forced oscillation?
An oscillation that is forced to oscillate at some frequency that is not it’s natural frequency.
The other frequency is known as the driving frequency.
In forcing oscillations, at what point should energy be added to the system?
Unless this is done at the natural frequency, the system is unlikely to undergo SHM and will dissipate the energy quite quickly.
This is what happens when you push a swing at the wrong moment.
What happens in damped oscillations?
Damped oscillations suffer a loss in energy at each oscillation and this reduces the amplitude over time.
Give an example of damping.
Attaching a small sail to a pendulum to catch air, this increases the air resistance artificially.
What is underdamping?
The oscillator completing several oscillations resulting in an exponential decrease in amplitude.
What is overdamping?
This happens when the amplitude of the oscillation drops so rapidly that the oscillator does not even complete one cycle.
How is can it be said that an oscillation has been critically damped?
If the damping is such that the oscillator returns to its equilibrium position in the quickest possible time, without going past that position(known as overshooting), then it’s critically damped.
What does the amount of damping change?
It changes how quickly the amplitude is reduced.
Give a consequence of too much overdamping.
It can cause the oscillator to take a very long time to return to it’s equilibrium position.
What is resonance?
If a system or object is forced to vibrate at its natural frequency, it will absorb more and more energy, which increases the amplitude of the oscillations. This is called resonance.
What happens as the driving frequency applied to an oscillating system changes?
It will pass through the natural frequency of the system, this results in large amplitude vibrations.
