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ResonanceNatural FrequencyAll objects have a natural frequency at which they will oscillate if disturbed.Examples:PendulumChild on a swingWine glassTuning forkBouncing ballHuman being?Tuning Fork Example!When objects are allowed to vibrate freely, they do so at their natural frequency

Eventually, all vibrations will fade.

How can you keep a vibration going?

Forced VibrationA forced vibration is one in which the object is continually pushed/vibrated in phase with the natural vibration in order to maintain or grow its motion.

Driving f versus Natural fWhen the frequency of the forced vibration (driving frequency) matches the natural frequency of the object, the object experiences RESONANCE.

Most often this involves oscillations with ever growing amplitude.Wine Glass Demo

Tacoma Narrows Bridge

1940 Tacoma Narrows Bridge Washington State wind matched the frequency of the bridge and caused it to be sent into a torsional vibration which destroyed the bridgehttp://www.youtube.com/watch?v=MBV-KA4ucSshttp://www.youtube.com/watch?v=aZQlmxrmjXQ

Human Resonance

Radio Stations

Resonance - The transfer of energy from one object to another having the same natural frequencySympathetic Vibration the response to a vibration with the same natural frequencyhttp://www.youtube.com/watch?v=zWKiWaiM3Pwhttp://www.youtube.com/watch?v=JDnNmLkQ3Bc

The Result of ResonanceWhen energy is transferred through resonance, the energy results in an increased amplitude of the vibrationIf we play our music louder and louder, the windows in your room will vibrate with a greater amplitude until they cant take it and they breakExamples Shimmy in your car at a certain speedWindows rattle as a large truck passes byEarthquakes/strong winds match the natural frequency of buildings/bridges and makes them vibrate and can make them crumble taken into account by architects

http://www.youtube.com/watch?v=3FM4E19PZhwhttp://www.youtube.com/watch?v=8Yx3nK7si-Q

Wacky ResonanceIn the world wars, soldiers used to march out of step over bridges so that it would not match the natural frequency of the bridge and make it crumble

During a street party in London, England calls were made to police about an earthquake in outlying areas created by the synchronization of the dancers that match the natural frequency of different parts of the city

Countering ResonanceWe use dampersA damper removes energy from a structure by absorbing itAn opera singer can get a glass to vibrate when he/she matches the correct natural frequency can break the glasshttp://www.youtube.com/watch?v=17tqXgvCN0E

Resonance in the Body:entire body 6 Hzhead 13 20 Hzeyes 35 75 HzLarge amplitude vibrations at any of these frequencies could irritate and/or damage parts of the bodyefforts are made to reduce vibrations in construction i.e. bulldozer, jackhammer etc.

Uses of Resonanceeggs exposed to ultrasound will resonate at a narrow range of frequencies if there is salmonella in the egg is vibrates at a different frequency and can be detected and thrown awaysame thing is used to detect the presence of biological and chemical warheads in a missile or artillery shell dont have to open it

Homework Provide definitions for the following terms in your own words: frequency, amplitude, forced vibration/driving frequency, in phase, resonance and sympathetic vibration.Explain how your friend pushing you on a swing relates to resonance. Use the terms frequency, amplitude, forced vibration/driving frequency, in phase, resonance and sympathetic vibration.Explain how a wine glass can shatter due to a persons voice. Use the terms frequency, amplitude, forced vibration/driving frequency, in phase, resonance and sympathetic vibration.Your friend is over at your house and starts playing the new Drake album. You notice when he plays his favourite song, the windows start vibrating. He wants to play it again and crank up the volume. Why is this a bad idea?Research dampers. What is their purpose? Draw a diagram of a vibration that is being dampened.