forced vibration

physics

Also known as: forced oscillation

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Last updated

June 26, 2026

Quick Summary

In physics, a forced vibration occurs when an external force continuously drives a system that is capable of vibrating. This is in contrast to free vibrations, which happen when a system is disturbed and then allowed to move without external influence.1

A key concept related to forced vibrations is resonance. This phenomenon happens when the frequency of the external driving force matches the natural frequency of the system's free vibrations. When resonance occurs, the system absorbs energy rapidly, leading to a significant increase in the amplitude of the vibrations. This effect can be observed in various situations, such as when a specific musical note can cause a glass to vibrate or when a bridge can be destroyed by soldiers marching in unison.12

Damping is also an important factor in forced vibrations. Damping refers to the dissipation of energy that causes vibrations to die down over time. While damping limits the amplitude of vibrations, especially during resonance, it is also crucial for preventing structures from shaking themselves apart due to constant external disturbances.34

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vibration
Forced vibrations occur if a system is continuously driven by an external agency. A simple example is a child’s swing that is pushed on each downswing. Of special interest are systems undergoing SHM and driven by sinusoidal forcing. This leads to the important phenomenon of…
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Forced vibrations occur if a system is continuously driven by an external agency. A simple example is a child’s swing that is pushed on each downswing. Of special interest are systems undergoing SHM and driven by sinusoidal forcing. This leads to the important phenomenon of…
Read More

mechanics
Damped and forced oscillations
Periodically forced oscillations may be represented mathematically by adding a term of the form a ₀ sin ωt to the right-hand side of equation (19). This term describes a force applied at frequency ω, with amplitude ma ₀. The result of applying such a force is…
Read More
Periodically forced oscillations may be represented mathematically by adding a term of the form a ₀ sin ωt to the right-hand side of equation (19). This term describes a force applied at frequency ω, with amplitude ma ₀. The result of applying such a force is…
Read More