Chapter13 MJM s7 9 Sound
Transcript of Chapter13 MJM s7 9 Sound
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Today 2/24/14
• Read Chapter 13.7 to 13.9 (p455 to 461)
• Watch the rest of this presentation
• Complete example problems in the book• Complete HW
– Given at the end of the presentation
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Raymond A. Serway
Chris Vuille
Chapter ThirteenVibrations and Waves
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Wave Motion
• A wave = the motion of a disturbance
• Mechanical waves require – Source of disturbance
– A medium that can be disturbed – Some physical connection within the medium which allows
influence to the rest of the medium
• All waves carry energy and momentum
Section 13.7
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Types of Waves – Traveling Waves
• Flip one end of a long rope thatis under tension and fixed at theother end
• The pulse travels to the rightwith a definite speed• A disturbance of this type is
called a traveling wave
Section 13.7
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Types of Waves – Transverse
• Transverse wave = each element disturbed moves in adirection perpendicular to the wave motion
Section 13.7
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Video of Transverse Wave
• https://www.youtube.com/watch?v=AtlxBODxWHc
• https://www.youtube.com/watch?v=Rbuhdo0AZDU
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Types of Waves – Longitudinal
• Longitudinal wave = elements of the medium aredisplaced parallel to the motion of the wave
• Also called a compression wave
Section 13.7
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Videos of Longitudinal Wave
• https://www.youtube.com/watch?v=ubRlaCCQfDk
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Waveform – A Picture of a Wave
• The brown curve is a“snapshot” of the wave atsome instant in time
• The blue curve is the samewave at a later time
• The high points are crests
• The low points are troughs
Section 13.7
Crest
Trough
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Longitudinal Wave Represented as a Sine Curve
• A longitudinal wave can also be represented as a sine curve• Compressions of coils correspond to crests
• Stretches areas of coil correspond to troughs• Also called density waves or pressure waves
Section 13.7
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Producing Waves
Section 13.8
• The blade vibrates causingoscillates in simple harmonicmotion in the string
• A steady stream of pulses on avery long string produces acontinuous wave
• Each small segment of the string,
such as P, oscillates with simpleharmonic motion
Blade
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Amplitude and Wavelength
• Amplitude = maximumdisplacement of string abovethe equilibrium position
• Wavelength (λ) = distancebetween two successivepoints that behave identically
• Period (T) = time it takes tomove through one cycle
• Frequency (ƒ) = vibrations perunit time (ƒ=1/T)
Section 13.8
Δy = amplitude Δx = wavelength
Equilibrium (X=0)
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Speed of a Wave on a String
• The speed on a wave stretched under sometension, F
– v = velocity (speed) – F = force (tension in the string)
– m is called the linear density (mass/unit Length)
• The speed depends only upon the propertiesof the medium – Ex: a denser medium will have less speed
Section 13.9
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Example Problems
• Now go back to the book and look overExample Problems 13.8, 13.9, 13.10
• This will prepare you to do your homework