18. Waves & Sound

Intro to Waves

Open Question
FIGURE EX15.7 is the position-versus-time graph of a particle in simple harmonic motion.a. What is the phase constant?
Open Question
An object in SHM oscillates with a period of 4.0 s and an amplitude of 10 cm. How long does the object take to move from x = 0.0 cm to x = 6.0 cm?
Open Question
FIGURE EX15.7 is the position-versus-time graph of a particle in simple harmonic motion.c. What is vₘₐₓ?
Open Question
The amplitude of an oscillator decreases to 36.8% of its initial value in 10.0 s. What is the value of the time constant?
Open Question
An object in simple harmonic motion has an amplitude of 8.0 cm, n angular frequency of 0.25 rad/s, and a phase constant of π rad. Draw a velocity graph showing two cycles of the motion.
Open Question
When a guitar string plays the note 'A,' the string vibrates at 440 Hz. What is the period of the vibration?
Open Question
The intensity of electromagnetic waves from the sun is 1.4 kW/m² just above the earth's atmosphere. Eighty percent of this reaches the surface at noon on a clear summer day. Suppose you think of your back as a 30 cm x 50 cm rectangle. How many joules of solar energy fall on your back as you work on your tan for 1.0 h?
Open Question
LASIK eye surgery uses pulses of laser light to shave off tissue from the cornea, reshaping it. A typical LASIK laser emits a 1.0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 15 ns and contains 1.0 mJ of light energy.b. During the very brief time of the pulse, what is the intensity of the light wave?
Open Question
A 2.0-m-long string vibrates at its second-harmonic frequency with a maximum amplitude of 2.0 cm. One end of the string is at x=0 cm . Find the oscillation amplitude at x=10 , 20, 30, 40, and 50 cm.
Open Question
The lowest note on a grand piano has a frequency of 27.5 Hz. The entire string is 2.00 m long and has a mass of 400 g. The vibrating section of the string is 1.90 m long. What tension is needed to tune this string properly?
Open Question
(II) P and S waves from an earthquake travel at different speeds, and this difference helps locate the earthquake “epicenter” (where the slippage took place).

(a) Assuming typical speeds of 8.5 km/s and 5.5 km/s for P and S waves, respectively, how far away did the earthquake occur if a particular seismic station detects the arrival of these two types of waves 1.5 min apart?
Open Question
(I) AM radio signals have frequencies between 550 kHz and 1600 kHz (kilohertz) and travel with a speed of 3.0 x 10⁸ m/s. What are the wavelengths of these signals? On FM the frequencies range from 88 MHz to 108 MHz (megahertz) and travel at the same speed. What are their wavelengths?
Open Question
(I) A fisherman notices that water wave crests pass the bow of his anchored boat every 3.0 s. He measures the distance between two crests to be 7.5 m. How fast are the waves traveling?
Open Question
I) A sound wave in air has a frequency of 265 Hz and travels with a speed of 343 m/s . How far apart are the wave crests (compressions)?
Open Question
The ripples in a certain groove 10.8 cm from the center of a 33-rpm vinyl phonograph record have a wavelength of 1.55 mm. What will be the frequency of the sound emitted?