3.6.1.4 - Forces Vibrations And Resonance Flashcards
What are free vibrations?
Involve no transfer of energy to or from the surrounding.
What is an example of free vibrations?
When you stretch and release a spring which oscillates at its natural frequency.
What are forced vibrations?
Happens when there is an external driving force.
What is the frequency of the force in forced vibrations called?
The driving frequency.
What is the natural frequency?
The frequency at which free oscillating systems oscillate at.
When does resonance occur?
When an oscillating system is forced to vibrate at a frequency close to its natural frequency. The amplitude of vibration increases rapidly to a maximum.
How are radios examples of resonance?
A radio is tuned so the electric circuit resonates at the same frequency as the radio station you want to listen to.
How is an organ pipe an example of resonance?
A column of air resonates in the pipe, driven by the motion of air at the base. This creates a stationary wave in the pipe.
What causes damping?
Decrease in amplitude of resonant vibration.
Decrease in frequency at which resonance occurs.
Describe the resonance peak when the system is lightly damped.
Have very sharp resonance peaks which increase dramatically in amplitude when the driving frequency is very close to the natural frequency.
Describe the resonance peaks when a system is heavily damped.
Have a flatter response. Amplitude doesn’t increase very much near the natural frequency and aren’t sensitive to the driving force.
How do structures susceptible to earthquakes use damping?
They use damping to avoid the effects of resonance. They use critical damping so that they move in the opposite direction to the shake caused by an earthquake.
How can damping be used to improve the performance of sound?
Sound waves produced by a loud speaker reflect of walls producing a stationary wave which affects the sound quality. Therefore recording studios use sound proofing on the walls to absorb sound energy.
