vibration
News •
-
What is vibration in physics?
In physics, vibration is the periodic back-and-forth motion of particles in an elastic body or medium. It typically happens when a physical system is displaced from its equilibrium and responds to forces that try to restore the equilibrium.
Vibrations can be free or forced. Free vibrations occur when a system is disturbed momentarily and then allowed to move without restraint, like a weight suspended from a spring. Forced vibrations happen when a system is continuously driven by an external agency, such as pushing a child's swing.
A key feature of free vibration is damping, where frictional forces gradually reduce the energy of the vibrations, causing the amplitude to decrease.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What causes objects to vibrate?
Vibration is the periodic back-and-forth movement of particles in an elastic object or medium, typically occurring when a physical system is disturbed from its equilibrium and responds to restoring forces.
Vibrations are classified as either free or forced. Free vibrations arise when a system is momentarily disturbed and then allowed to move freely. Forced vibrations occur when a system is continuously driven by an external force.
Resonance, a significant phenomenon, happens when the driving frequency approaches the natural frequency of free vibrations, leading to a rapid increase in the vibration amplitude.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What is the difference between a vibration and a wave?
Vibration is the periodic back-and-forth movement of particles in an elastic body or medium, typically when a physical system is disturbed from equilibrium. Examples include a struck metal block or a weight suspended from a spring.
A wave is a disturbance that propagates energy through a medium or space. Sound and light both travel as waves. Sound waves are disturbances that move through a medium by causing particles to vibrate.
Thus, vibrations are localized particle movements, while waves are the propagation of these disturbances from place to place.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are examples of vibrating objects in everyday life?
Vibration is the periodic back-and-forth motion of particles in an elastic body or medium, typically when a physical system is disturbed from equilibrium. Vibrating objects are common in everyday life; here are some examples:
- Musical Instruments The motion of strings, membranes, and air columns consists of a superposition of simple harmonic motions.
- Bridges Traffic, wind, or earthquakes can cause bridge oscillations, which are vibrations that can lead to structural failure.
- Electronics Circuits containing inductance and capacitance can produce electrical vibrations involving sinusoidal current flow.
- Tools Extensive use of vibratory hand tools like chain saws and pneumatic drills can cause vibration white finger (VWF) in workers.
6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does the frequency of vibration affect the sound we hear?
Sound travels in waves, which are disturbances causing particles to vibrate. Frequency, measured in hertz (Hz), determines the pitch of the sound.
Higher frequencies correspond to higher pitches, while lower frequencies correspond to lower pitches. Humans can typically hear frequencies ranging from about 20 Hz to 20,000 Hz (20 kHz). The ear's frequency response is nonlinear, meaning that it responds to frequency ratios rather than absolute frequency differences.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are resonance and damping in relation to vibration?
Resonance in physics is the amplified response of a system vibrating in sync with an external force. This can be seen in musical instruments or, destructively, in bridges.
Damping is the reduction of vibratory motion through energy dissipation. For example, shock absorbers in cars use damping. Systems can be critically damped to prevent vibration, overdamped for controlled motion, or underdamped to gradually reduce vibrations.
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
vibration, periodic back-and-forth motion of the particles of an elastic body or medium, commonly resulting when almost any physical system is displaced from its equilibrium condition and allowed to respond to the forces that tend to restore equilibrium.
Vibrations fall into two categories: free and forced. Free vibrations occur when the system is disturbed momentarily and then allowed to move without restraint. A classic example is provided by a weight suspended from a spring. In equilibrium, the system has minimum energy and the weight is at rest. If the weight is pulled down and released, the system will respond by vibrating vertically.
The vibrations of a spring are of a particularly simple kind known as simple harmonic motion (SHM). This occurs whenever the disturbance to the system is countered by a restoring force that is exactly proportional to the degree of disturbance. In this case, the restoring force is the tension or compression in the spring, which (according to Hooke’s law) is proportional to the displacement of the spring. In simple harmonic motion, the periodic oscillations are of the mathematical form called sinusoidal.
" height="20" alt="HEW Logo">
Most systems that suffer small disturbances counter them by exerting some form of restoring force. It is frequently a good approximation to suppose that the force is proportional to the disturbance, so that SHM is, in the limiting case of small disturbances, a generic feature of vibrating systems. One characteristic of SHM is that the period of the vibration is independent of its amplitude. Such systems therefore are used in regulating clocks. The oscillation of a pendulum, for instance, approximates SHM if the amplitude is small.
A universal feature of free vibration is damping. All systems are subject to frictional forces, and these steadily sap the energy of the vibrations, causing the amplitude to diminish, usually exponentially. The motion is therefore never precisely sinusoidal. Thus, a swinging pendulum, left undriven, will eventually return to rest at the equilibrium (minimum-energy) position.
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 resonance. Resonance occurs when the driving frequency approaches the natural frequency of free vibrations. The result is a rapid take-up of energy by the vibrating system, with an attendant growth of the vibration amplitude. Ultimately, the growth in amplitude is limited by the presence of damping, but the response can, in practice, be very great. It is said that soldiers marching across a bridge can set up resonant vibrations sufficient to destroy the structure. Similar folklore exists about opera singers shattering wine glasses.
Electric vibrations play an important role in electronics. A circuit containing both inductance and capacitance can support the electrical equivalent of SHM involving sinusoidal current flow. Resonance occurs if the circuit is driven by alternating current that is matched in frequency to that of the free oscillations of the circuit. This is the principle behind tuning. For example, a radio receiver contains a circuit, the natural frequency of which can be varied. When the frequency matches that of the radio transmitter, resonance occurs and a large alternating current of that frequency develops in the circuit. In this way, resonating circuits can be used to filter out one frequency from a mixture.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
In musical instruments, the motion of strings, membranes, and air columns consists of a superposition of SHM’s; in engineering structures, vibrations are a common, though usually undesirable, feature. In many cases, complicated periodic motions can be understood as the superposition of SHM at many different frequencies.