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The pressure in a traveling sound wave is given by the equation $$ \Delta p=(1.50 \mathrm{~Pa}) \sin \pi\left[\left(0.900 \mathrm{~m}^{-1}\right) x-\left(315 \mathrm{~s}^{-1}\right) t\right] $$ Find the (a) pressure amplitude, (b) frequency, (c) wavelength, and (d) speed of the wave.

Short Answer

Expert verified
(a) 1.50 Pa, (b) 50.2 Hz, (c) 6.98 m, (d) 350.4 m/s.

Step by step solution

01

Find Pressure Amplitude

The pressure amplitude is the maximum change in pressure, which is given directly in the wave equation as the coefficient of the sine function. Thus, the pressure amplitude is \(1.50 \, \text{Pa}\).
02

Find Angular Frequency

The wave equation is of the form \( \Delta p = A \sin (kx - \omega t) \), where \( \omega \) is the angular frequency. By comparing this with the provided equation, \( \omega = 315 \, \text{s}^{-1} \).
03

Calculate Frequency

Frequency \( f \) is related to angular frequency \( \omega \) by the formula \( \omega = 2 \pi f \). So, we find \( f = \frac{\omega}{2\pi} = \frac{315}{2\pi} \approx 50.2 \, \text{Hz} \).
04

Find Wave Number

The wave number \( k \) is given in the wave equation as \( 0.900 \, \text{m}^{-1} \).
05

Calculate Wavelength

Wavelength \( \lambda \) is related to the wave number \( k \) by \( k = \frac{2\pi}{\lambda} \). Solving for \( \lambda \), we have \( \lambda = \frac{2\pi}{k} = \frac{2\pi}{0.900} \approx 6.98 \, \text{m} \).
06

Calculate Speed of the Wave

The speed \( v \) of the wave can be calculated using the equation \( v = f \lambda \). Substituting the known values, \( v = 50.2 \times 6.98 \approx 350.4 \, \text{m/s} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Pressure Amplitude
In a sound wave, the pressure amplitude represents the maximum change in pressure from the ambient atmospheric pressure due to the wave. It essentially measures how intense or loud the sound is perceived.

In our given sound wave equation, the pressure amplitude is the coefficient of the sine function. This means it's the number that multiplies the sine part of the equation itself, which indicates the peak deviation from the standard pressure. In this particular equation, the pressure amplitude is directly given as \(1.50 \, \text{Pa}\). This value tells us the greatest extent, in pascals, to which the pressure changes above and below the normal atmospheric pressure as the wave passes through a medium.
Angular Frequency
Angular frequency is a crucial concept for understanding how fast the sound wave oscillates over time. It is denoted by \( \omega \) and is measured in radians per second (s\(^{-1}\)).

In the context of the wave equation, angular frequency shows up as a part of the term that multiplies time \( t \). Specifically, it was identified as \( 315 \, \text{s}^{-1} \) in the equation \( \Delta p = (1.50 \, \text{Pa}) \sin \pi [0.900 \, \text{m}^{-1} x - 315 \, \text{s}^{-1} t ] \). This value represents how quickly the sine wave oscillates as time progresses.
  • Angular frequency is linked to the physical frequency of the wave (\( f \)) by the formula \( \omega = 2 \pi f \).
  • In this exercise, using this relationship helps derive the frequency of the wave which was calculated as approximately \( 50.2 \, \text{Hz} \).
Wavelength
The wavelength of a sound wave, denoted by \( \lambda \), is the physical distance over which the wave's shape repeats itself. Long wavelengths correspond to lower frequencies, and vice versa.

Wavelength is naturally tied to the wave number \( k \), which is derived through the relationship \( k = \frac{2\pi}{\lambda} \). In this particular problem, the wave number was provided as \( 0.900 \, \text{m}^{-1} \). Solving for the wavelength using \( \lambda = \frac{2\pi}{k} \), we find it to be approximately \( 6.98 \, \text{m} \).

Having the wavelength gives us insight into the size of the sound wave in spatial terms. It tells us how far the sound travels before the pattern begins to repeat.
Speed of Sound Wave
The speed of a sound wave, represented by \( v \), describes how quickly the sound wave propagates through a medium. It's an essential parameter because it tells us how fast the sound reaches our ears or detectors.

The formula connecting speed with frequency and wavelength is \( v = f \lambda \). From the exercise, the calculated frequency \( f \) is approximately \( 50.2 \, \text{Hz} \), and the wavelength \( \lambda \) is approximately \( 6.98 \, \text{m} \). Plugging these into the formula, we find the speed of the wave to be about \( 350.4 \, \text{m/s} \).
  • This speed could vary depending on factors like temperature and medium (air, water, etc.).
  • In most exercises involving ideal conditions, the calculated speed aligns closely with the standard speed of sound in air, which is approximately \( 343 \, \text{m/s} \) at room temperature.

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Most popular questions from this chapter

A police car is chasing a speeding Porsche 911 . Assume that the Porsche's maximum speed is \(80.0 \mathrm{~m} / \mathrm{s}\) and the police car's is \(54.0 \mathrm{~m} / \mathrm{s}\). At the moment both cars reach their maximum speed, what frequency will the Porsche driver hear if the frequency of the police car's siren is \(440 \mathrm{~Hz}\) ? Take the speed of sound in air to be \(340 \mathrm{~m} / \mathrm{s}\).

A continuous sinusoidal longitudinal wave is sent along a very long coiled spring from an attached oscillating source. The wave travels in the negative direction of an \(x\) axis; the source frequency is \(25 \mathrm{~Hz}\); at any instant the distance between successive points of maximum expansion in the spring is \(24 \mathrm{~cm} ;\) the maximum longitudinal displacement of a spring particle is \(0.30 \mathrm{~cm} ;\) and the particle at \(x=0\) has zero displacement at time \(t=0 .\) If the wave is written in the form \(s(x, t)=s_{m} \cos (k x \pm \omega t),\) what are (a) \(s_{m},\) (b) \(k,\) (c) \(\omega\), (d) the wave speed, and (e) the correct choice of sign in front of \(\omega ?\)

A state trooper chases a speeder along a straight road; both vehicles move at \(160 \mathrm{~km} / \mathrm{h}\). The siren on the trooper's vehicle produces sound at a frequency of \(500 \mathrm{~Hz}\). What is the Doppler shift in the frequency heard by the speeder?

A whistle of frequency \(540 \mathrm{~Hz}\) moves in a circle of radius \(60.0 \mathrm{~cm}\) at an angular speed of \(15.0 \mathrm{rad} / \mathrm{s}\). What are the (a) lowest and (b) highest frequencies heard by a listener a long distance away, at rest with respect to the center of the circle?

Approximately a third of people with normal hearing have ears that continuously emit a low-intensity sound outward through the ear canal. A person with such spontaneous otoacoustic emission is rarely aware of the sound, except perhaps in a noisefree environment, but occasionally the emission is loud enough to be heard by someone else nearby. In one observation, the sound wave had a frequency of \(1665 \mathrm{~Hz}\) and a pressure amplitude of \(1.13 \times 10^{-3} \mathrm{~Pa}\). What were (a) the displacement amplitude and (b) the intensity of the wave emitted by the ear?

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