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Chapter 25 Vibrations & Waves

Chapter 25 Vibrations & Waves. Conceptual Physics 1999 Hewitt Bloom High School. Definitions. Vibration - a wiggle in time Atoms Wave - a wiggle in space and time Earthquakes, water, sound, etc. 25.1 Vibration of a Pendulum. Period , T (s)- time required for one complete cycle

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Chapter 25 Vibrations & Waves

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  1. Chapter 25Vibrations & Waves Conceptual Physics 1999 Hewitt Bloom High School

  2. Definitions • Vibration- a wiggle in time • Atoms • Wave- a wiggle in space and time • Earthquakes, water, sound, etc.

  3. 25.1 Vibration of a Pendulum • Period, T (s)- time required for one complete cycle • Back and forth • Two pendulums of the same length have the same period, regardless of mass • Longer pendulum string- longer T • Shorter string, shorter T

  4. 25.2 Wave Description • Simple Harmonic Motion (SHM)- back-and-forth motion vibratory motion • Sine curve- shape traced out when a pendulum is followed • P. 373 Figure 25.2 • Physics Physlets P.16.9 (Animation 3) • Wave on a String Phet • Frequency, f (Hertz, Hz)- number of cycles per second • Inverse relationship to period (T) • f=1/T and T=1/f

  5. Sine Waves • Crest- top-most portion of a wave • Trough- bottom-most portion of a wave • Amplitude (A)- vertical distance measured from equilibrium to a crest • Wavelength (l)- horizontal distance from crest-to-crest or trough-to-trough

  6. 25.3 Wave Motion • Energy transfer with a medium • Energy is transferred by a disturbance in the medium, not the particles in the medium moving • Sound- compression of air molecules in waves • Earthquake- compression of Earth or rise-and-fall of Earth • Energy can be transferred without a medium • Light- oscillation of electromagnetic energy • As well as X-rays, infrared, microwaves, FM, AM, etc.

  7. 25.4 Wave Speed • Regardless of medium, wavelength and frequency are needed • Speed = distance ÷ time • Speed = wavelength ÷ period = wavelength • frequency • v = l/T = l • f • Speed of sound in air ranges from 340-350 m/s • Temperature dependant

  8. 25.5 Transverse Waves • Transverse waves- motion of the medium moves perpendicularly to the direction the energy travels • Ropes, surface water waves, stringed instruments • Electromagnetic waves • Physics Physlets I.17.1 (Animation 1 & 2)

  9. 25.6 Longitudinal Waves • Longitudinal waves- motion of the medium moves parallel to the direction the energy travels • Slinky pulled back • Physics Physets I.17.1 (Animation 3)

  10. 25.6 Interference • Interference pattern- waves from two separate sources overlapping • Constructive interference- the crest of one wave overlaps with the crest of another wave • In Phase- Increases amplitude • Physics Physlet I.17.3 (Animation 1) • Destructive interference- the crest of one wave overlaps with the trough of another wave • Out of Phase- Decreases amplitude • Physics Phslets I.17.3 (Animation 2)

  11. Interference Pattern

  12. 25.8 Standing Waves • Standing waves- when the incident and reflected waves overlap • Nodes- the portion of the waves that remain stationary • Antinodes- the portion of the waves that have the largest disturbance • http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave4.html

  13. 25.9 Doppler Effect • Doppler Shift- change in frequency due to motion between the sound source and receiver • Physics Physlet I.18.4 (Animation 4) • Motion only depends on the objects getting closer or further away. It doesn’t matter who does which. • Blue Shift • Source stationary, receiver moving towards source • Receiver stationary, source moving towards receiver • Red Shift • Source stationary, receiver moving away from source • Receiver stationary, source moving away from receiver

  14. Doppler Shift (Sound & Light)

  15. 25.10 Bow Waves • Bow waves- Constructive interference in water as created by an object moving faster than the waters’ speed • 2D wave

  16. 25.11 Shock Waves • Shock waves- Constructive interference in air as created by an object moving faster than the speed of sound • 3D wave • Sonic Boom- increased amplitude of so many waves arriving at our ears all at one time • Physics Physlet I.18.4 (Animation 5)

  17. Terms (lots of ‘em) • Amplitude • Antinodes • Blue shift • Bow wave • Constructive interference • Crest • Destructive interference • Doppler effect • Frequency • Hertz • In phase • Interference pattern • Longitudinal wave • Node • Out of phase • Period • Red shift • Shock wave • Simple harmonic motion • Sine curve • Sonic boom • Standing wave • Transverse wave • Trough • Vibration • Wave • Wavelength

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