Resonance
The phenomenon where an oscillating system driven at its natural frequency absorbs maximum energy, resulting in large-amplitude vibrations.
Governing formula
f_driven = f_natural = (1 / 2π) √(k / m)
SI unit
Hz
In depth
At resonance, driving force inputs energy in phase with system velocity, minimizing destructive damping and driving vibration amplitude to its peak limits.
Examples in the real world
Pushing a playground swing at the top of its arc to increase height, or the Tacoma Narrows Bridge collapsing under wind-driven aeroelastic resonance.