Define oscillation
Periodic to-and-fro motion of an object between 2 limits
Define simple harmonic motion
Oscillatory motion of a particle whose acceleration is directly proportional to its displacement from a fixed point and this acceleration is always in opposite direction to its displacement
Define free oscillation
Object oscillates with no energy gain or loss, oscillating with constant amplitude as there is no external force acting on it
Define damping
Process where energy is taken from an oscillating system as a result of dissipative forces
Define a damped oscillation
Occurs when there is a continuous dissipation of energy to the surroundings such that total energy decreases with time, hence amplitude of oscillation progressively decreases
Explain light damping
- Object undergoes a number of oscillations
- Amplitude decreases exponentially with time
eg. Spring-mass system
Explain critical damping
- No oscillations occur
- Displacement brought to zero in shortest possible time
eg. Car suspension system
Explain heavy damping
- No oscillations occur when damping force exceeds point of critical damping
- System takes a long time to return to equilibrium position
eg. Door closer with hydraulic damper
Explain a car suspension system
- Good suspension system is critically damped
- Shock absorbers on a car critically damp the suspension of the whole vehicle
- Lightly damped suspension will cause passengers to be thrown around as system needs time to stop oscillating
- Heavily damped system will stay compressed for awhile
What other things are critically damped
Analogue voltmeters and ammeters
Define forced oscillations
Oscillations caused by continual input of energy by external applied force to compensate the loss due to damping, to maintain amplitude
Define resonance
Occurs when the resulting amplitude of system become a maximum when driving frequency of external force equals to natural frequency of system, so there is maximum transfer of energy from external force to system
What does the amplitude of a forced oscillations depend on
- Damping of the system
- Relative values of driving and natural frequency
What happens when damping increases
- Lower and flatter peak amplitudes at all frequencies
When is maximum amplitude of a forced oscillations reached
Driving frequency slightly less than natural frequency
What are the useful applications of resonance
- Radio
- Musical instruments
