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P H Y S I C SChapter 7: Waves and Vibrations

Section 7C: Wave Properties and SoundMechanical WaveA disturbance that travels through a mediumi.e. Sound requires medium of air or water

What is a Wave?

Mechanical WaveWaves transfer energy and not matter

Sine WaveWave motion can be mathematically described by a sine or cosine wave

Two Types of WavesTransverse disturbance is perpendicular to motionLongitudinal disturbance is parallel to motion

Slinky DemonstrationEnergy is transported not matterTransverse vs. Longitudinal

Parts of a WaveWavelength () distance in one cycleAmplitude displacementCrest high pointTrough low point

Note: LambdaSound Waves and Tuning Fork DemonstrationFrequency Pitch Amplitude Volume

Note: Frequency is wave cycles per second (Hz)

512 Hz

1024 Hz

2048 Hz9Speed of SoundNote: Sound travels faster in solids, liquids and gas respectivelyTempSpeed-10o C325 m/s0o C331 m/s10o C337 m/s20o C343 m/s30o C349 m/sMediumSpeedAir (20o C)343 m/sHelium972 m/sAlcohol1,143 m/sWater1,493 m/sIron5,130 m/sPyrex Glass5,640 m/sDiamond12,000 m/sWave Speed EquationFrequency Equation

In-Class Problem #1Determine the (a) number of waves, (b) wavelength, (c) amplitude, (d) frequency, (e) period and (f) wave speed.

In-Class Problem #1Determine the (a) number of waves, (b) wavelength, (c) amplitude, (d) frequency, (e) period and (f) wave speed.

waves = 2 = 0.04 mA = 0.02 mf = 0.4 HzT = 2.5 sv = 0.016 m/s

In-Class Problem #2A toy boat in the ocean rises every 3.0 s as wave crests pass by. The distance between wave crests is 5.0 m. Determine the (a) frequency, (b) period, (c) the wave length and (d) how fast are the waves traveling.

In-Class Problem #2A toy boat in the ocean rises every 3.0 s as wave crests pass by. The distance between wave crests is 5.0 m. Determine the (a) frequency, (b) period, (c) the wave length and (d) how fast are the waves traveling.

f = 0.33 Hz = 5.0 mT = 3.0 s v = 1.65 m/s

AssignmentProblem Set 7C7C-7D Quiz (Wave Properties and Behavior)