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is another simple example of a resonant system with which most people have practical experience. It is a form of pendulum. If the system is excited (pushed) with a period between pushes equal to the inverse of the pendulum's natural frequency, the swing will swing higher and higher, but if excited at
594:
by subjecting it to a vibratory force for determining qualities, characteristics, or conditions thereof, or sensing, studying or making analysis of the vibrations otherwise generated in or existing in the article or mechanism. Devices include right methods to cause vibrations at a natural mechanical
329:
Some resonant objects have more than one resonance frequency, particularly at harmonics (multiples) of the strongest resonance. It will vibrate easily at those frequencies, and less so at other frequencies. It will "pick out" its resonance frequency from a complex excitation, such as an impulse or a
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Various method of inducing mechanical resonance in a medium exist. Mechanical waves can be generated in a medium by subjecting an electromechanical element to an alternating electric field having a frequency which induces mechanical resonance and is below any electrical resonance frequency. Such
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and its height above the lowest point. As the bob descends and picks up speed, its potential energy is gradually converted to kinetic energy (energy of movement), which is proportional to the bob's mass and to the square of its speed. When the bob is at the bottom of its travel, it has maximum
514:, is sometimes characterized in physics textbooks as a classic example of resonance. The catastrophic vibrations that destroyed the bridge were due to an oscillation caused by interactions between the bridge and the winds passing through its structure—a phenomenon known as
71:) closer than it does other frequencies. It may cause violent swaying motions and potentially catastrophic failure in improperly constructed structures including bridges, buildings and airplanes. This is a phenomenon known as resonance disaster.
98:
designing objects that have engines must ensure that the mechanical resonant frequencies of the component parts do not match driving vibrational frequencies of the motors or other strongly oscillating parts.
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wideband noise excitation. In effect, it is filtering out all frequencies other than its resonance. In the example above, the swing cannot easily be excited by harmonic frequencies, but can be excited by
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a different frequency, it will be difficult to move. The resonance frequency of a pendulum, the only frequency at which it will vibrate, is given approximately, for small displacements, by the equation:
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devices can apply mechanical energy from an external source to an element to mechanically stress the element or apply mechanical energy produced by the element to an external load.
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of the vibration and stores it there. Because of this repeated storage and additional energy input the system swings ever more strongly, until its load limit is exceeded.
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energy (a form of potential energy) when the bob is instantaneously motionless at the top of its swing. This energy is proportional to both the mass of the
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Many resonant objects have more than one resonance frequency. Such objects will vibrate easily at those frequencies, and less so at other frequencies. Many
90:—to modify the response at resonance. The structure is also designed to resonate at a frequency which does not typically occur. Buildings in
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kinetic energy and minimum potential energy. The same process then happens in reverse as the bob climbs towards the top of its swing.
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A method for determining mechanical resonance frequencies and for calculating elastic moduli from these frequencies
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This article is about mechanical resonance in physics and engineering. For a general description of resonance, see
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452:/mass system stores energy as tension in the spring, which is ultimately stored as the energy of bonds between
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yields a description for any displacement). Note that, in this approximation, the frequency does not depend on
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The natural frequency of the very simple mechanical system consisting of a weight suspended by a spring is:
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Resonance may cause violent swaying motions in constructed structures, such as bridges and buildings. The
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zones are often constructed to take into account the oscillating frequencies of expected ground motion.
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The dramatic, rhythmic twisting that resulted in the 1940 collapse of "Galloping Gertie", the original
218:) increases its natural frequency, which is a general characteristic of vibrating mechanical systems.
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describes the destruction of a building or a technical mechanism by induced vibrations at a system's
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590:. This subclass is itself indented under subclass 570, Vibration. Such devices test an article or
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Resonances excited by marching soldiers have caused several bridge collapses. This sign on the
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Avoiding resonance disasters is a major concern in every building, tower and bridge
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Apparatus and method for suppressing mechanical resonance in a mass transit vehicle
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393:
383:
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75:
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448:). Mechanical systems store potential energy in different forms. For example, a
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A wineglass breaking when someone sings a loud note at exactly the right pitch.
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form and back again. In the pendulum, for example, all the energy is stored as
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Resonance, Tacoma
Narrows Bridge Failure, and Undergraduate Physics Textbooks
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522:, father of the field of bridge aerodynamics, wrote an article about this.
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Tuned ground motion detector utilizing principles of mechanical resonance
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the resonance made. Various devices study the amplitude response over a
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classifies devices that tests mechanical resonance under subclass 579,
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20:. For mechanical resonance of sound including musical instruments, see
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characteristics measured under predetermined vibration conditions.
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Allensworth, et al., United States Patent 4,524,295. June 18, 1985
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Mechanical resonators work by transferring energy repeatedly from
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A mechanical resonance apparatus for undergraduate laboratories
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is the length from the pivot point to the center of mass. (An
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of its oscillations matches the system's natural frequency of
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Apparatus for determining the behavior of suspended cables
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Vibrating-blade relays with electro-mechanical resonance
24:. For the music album by American rock band Tesla, see
198:. For a given mass, stiffening the system (increasing
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204:
135:
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Apparatus and method for generating mechanical waves
272:{\displaystyle f={1 \over 2\pi }{\sqrt {g \over L}}}
172:{\displaystyle f={1 \over 2\pi }{\sqrt {k \over m}}}
356:Various examples of mechanical resonance include:
271:
210:
171:
788:Apparatus for testing textiles and like materials
488:. Periodic excitation optimally transfers to the
884:Method of controlling mechanical resonance hand
772:Method and apparatus for inspecting materials
749:. American Society for testing and materials.
8:
472:warns soldiers to break step when crossing.
804:Method and apparatus for testing materials
82:building for instance relies on a 660-ton
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53:to respond at greater amplitude when the
290:(about 9.8 m/s near the surface of
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374:keep time by mechanical resonance in a
106:keep time by mechanical resonance in a
828:Mechanical resonance detection systems
7:
844:Quantum mechanical resonance devices
756:. American Journal of Physics, 1995.
42:in a mechanical oscillatory system
14:
693:K. Billah and R. Scanlan (1991),
546:Königs Wusterhausen Central Tower
535:(due to soldiers walking in step)
476:In mechanics and construction a
724:Class 73, Measuring and testing
31:Tendency of a mechanical system
860:Piezoelectric resonance device
852:Mechanical resonance indicator
780:Apparatus for testing textiles
484:frequency, which causes it to
1:
796:Testing and adjusting device
506:Tacoma Narrows Bridge (1940)
434:London Millennium Footbridge
26:Mechanical Resonance (album)
699:American Journal of Physics
568:United States Patent Office
533:Broughton Suspension Bridge
442:Broughton Suspension Bridge
288:acceleration due to gravity
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639:List of laser applications
595:resonance and measure the
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351:California Science Center
38:Graph showing mechanical
812:Article testing machine
607:is made. This includes
912:Earthquake engineering
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907:Mechanical vibrations
889:U.S. patent 7,027,897
881:U.S. patent 4,958,113
873:U.S. patent 4,524,295
865:U.S. patent 3,990,039
857:U.S. patent 3,141,100
849:U.S. patent 3,044,290
841:U.S. patent 2,948,861
833:U.S. patent 2,918,589
825:U.S. patent 2,729,972
817:U.S. patent 2,539,954
809:U.S. patent 2,352,880
801:U.S. patent 1,990,085
793:U.S. patent 1,930,267
785:U.S. patent 1,598,141
777:U.S. patent 1,517,911
769:U.S. patent 1,414,077
745:S Spinner, WE Tefft,
659:Sympathetic resonance
512:Tacoma Narrows Bridge
500:Tacoma Narrows Bridge
470:Albert Bridge, London
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417:The resonance of the
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49:is the tendency of a
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683:Mechanical resonance
634:Electrical resonance
582:study, of Class 73,
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47:Mechanical resonance
516:aeroelastic flutter
361:Musical instruments
64:resonance frequency
729:2007-05-13 at the
629:Dunkerley's method
478:resonance disaster
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460:Resonance disaster
365:acoustic resonance
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69:resonant frequency
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22:Acoustic resonance
701:, 59(2), 118–124
644:Mechanical filter
552:Millennium Bridge
550:Resonance of the
520:Robert H. Scanlan
400:Orbital resonance
300:elliptic integral
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558:Applications
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538:Collapse of
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649:Reed switch
349:exhibit at
122:Description
901:Categories
752:CC Jones,
664:Transducer
80:Taipei 101
917:Resonance
654:Resonator
601:amplitude
597:frequency
592:mechanism
584:Measuring
580:amplitude
576:frequency
572:resonance
486:oscillate
315:potential
252:π
223:swing set
152:π
96:Engineers
59:vibration
55:frequency
40:resonance
18:Resonance
727:Archived
623:See also
482:resonant
380:pendulum
338:Examples
112:pendulum
84:pendulum
761:Patents
722:USPTO,
599:and/or
588:testing
421:in the
406:of the
392:of the
311:kinetic
294:), and
286:is the
194:is the
186:is the
92:seismic
615:, and
494:energy
490:system
450:spring
372:clocks
282:where
182:where
104:clocks
703:(PDF)
670:Notes
578:, or
454:atoms
404:moons
382:, or
370:Most
292:Earth
114:, or
61:(its
586:and
566:The
492:the
444:and
304:mass
190:and
188:mass
423:ear
410:'s
323:bob
313:to
86:—a
67:or
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221:A
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363:(
296:L
284:g
264:L
261:g
249:2
245:1
240:=
237:f
206:k
192:k
184:m
164:m
161:k
149:2
145:1
140:=
137:f
28:.
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