- Resonance occurs when the frequency of an applied force to an oscillating system (driving frequency) is equal to its natural frequency
- The mathematics to describe this are complex but can be best appreciated by considering a child being pushed on a swing:
- The child and swing have a fixed natural frequency
- Every time the child is pushed, energy is added to the system
- When the timing of the push (driving frequency) matches exactly the natural frequency of the swing:
- Every push will be at the time of the child moving forward
- All energy inputted works to increase the height of the swing (and thus increase the amplitude of the system)
- Results in energy being added most efficiently
- When the timing of the push (driving frequency) does not match the natural frequency of the swing:
- Some pushes will be timed when the child is swinging forward but some will be timed when the child is swinging backwards
- Results in some energy being used to resist movement of the swing (and thus decrease the amplitude of the system)
- Thus, energy is added to the system inefficiently
