Resonance
each oscillating system has its distinctive, natural frequency : fn
driving an oscillator with a frequency which is strongly different of this is usually not effective
driving the system with a frequency close to its natural frequency increases strongly the amplitude--> this phenomenon is called RESONANCE
resonance type increases can be achieved also by driving with with frequencies with integer parts of fn
complex systems have all natural frequencies (depends on the stiffness of material, the mass, size and form of the objects)
good effects of resonance: tuning the radio, tuning musical instruments, etc ….
bad effects of resonance: safety of buildings, bridges, airplanes etc.