Oscillations Flashcards
Free vibrations
Not influenced by any external varying force
Forced vibrations
System made to oscillate by an external periodic force
eg a loudspeaker made to oscillate by the oscillating electrical signal from an amplifier
Damping
Energy lost in simple harmonic motion due to frictional forces
Light damping
Oscillations take a long time to fade away
Heavy damping
Object hardly oscillates
Critical Damping
Object returned to its equilibrium point without oscillating in the quickest possible time
If something is damped, what happens to its amplitude and where does this occur?
Amplitude less at maximum point. This occurs at a lower frequency.
Resonance and example
Driving frequency is the same as natural frequency, thus amplitude increases and increases.
eg seats rattling on a bus
Barton’s Pendulum
Larger pendulum provides a driving frequency.
Pendulum which matches length of this pendulum oscillates with a greater frequency, as it is resonating.
All pendulums oscillate a bit. This is forced vibration.
How can Barton’s Pendulum experiment be used
To experiment the effect of damping.
Length of driver pendulum is changed and damping can be added to the smaller pendulums. For example, cardboard fins to increases air resistance.
Uses of resonance
Standing waves in pipes
Clocks and watches- quartz crystals resonate, producing accurate timing frequencies
Ultra-sonic cleaning- dirt particles resonate with the applied frequency and are dislodged
Crystal radios- circuits resonate at the same frequency as a radio station
Radio antennas (aerials)- resonate when they interact with radio waves
Why mass oscillates with SHM when displaced from equilibrium and released
Force is proportional to displacement from equilibrium position
Force is always in opposite direction to displacement
