Finding Displacement Amplitude of a Pressure Wave

In summary, a traveling sound wave can be described by the equation ∆P = 20.0 sin(15.5x − 5.32 × 103t ), where x is in meters, t is in seconds, and pressure is in pascals. To find the displacement amplitude, we can use the formula ∆Pmax = ρvωsmax, where ρ is the density of air, v is the velocity of the wave, and ω is the angular frequency. By setting the sine function equal to its maximum value of 1, we can solve for the displacement amplitude, which is equal to 1.53 x 10^-7 meters. However, in this case, the correct
  • #1
roam
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Homework Statement



A traveling sound wave causes a variation in air pressure according to the equation:

∆P = 20.0 sin(15.5x − 5.32 × 103t )

where x is in metres, t in seconds and pressure is in pascals.

What is the amplitude of the displacement of the air particles caused by this pressure wave (i.e. the displacement amplitude)?

Take ρair=1.21 kgm–3.

Homework Equations



Pressure amplitude is related to displacement amplitude by

[tex]\Delta P_{max}= \rho v \omega s_{max}[/tex]

The Attempt at a Solution



I know that the angular frequency ω of the pressure wave is 5320.0 rads–1, and the velocity v of the pressure wave is 343.0 ms–1. But I can't use the formula above because I can't determine the value of [tex]\Delta P_{max}[/tex].

How can I find [tex]\Delta P_{max}[/tex] from

∆P = 20.0 sin(15.5x − 5.32 × 103t )

when I don't know the values of "x" and "t"? What values do I need to substitute there?
 
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  • #2
∆P is sinusoidal, what is the maximum value that sine of anything can take?
 
  • #3
rock.freak667 said:
∆P is sinusoidal, what is the maximum value that sine of anything can take?

I think the maximum value for sine is 1. So we must have:

(15.5x − 5.32 × 103t ) =1

Okay, then we get:

∆Pmax = 20.0 sin(1)= 0.34

[tex]\Delta P_{max}= \rho v \omega s_{max}[/tex]

[tex]0.34= 1.21 \times 343 \times 5320 S_{max}[/tex]

[tex]S_{max} = \frac{0.34}{2207959.6}= 1.53 \times 10^{-7} [/tex]

But this is not the correct answer, the correct answer must be 9.05 μm. What am I doing wrong here??
 
  • #4
roam said:
I think the maximum value for sine is 1.

Yes.


roam said:
So we must have:

(15.5x − 5.32 × 103t ) =1


If the maximum of sine is 1, then shouldn't sin(15.5x − 5.32 × 103t ) =1?
 
  • #5
Thank you so much! :redface:
 

FAQ: Finding Displacement Amplitude of a Pressure Wave

1. What is displacement amplitude?

Displacement amplitude refers to the maximum distance a particle or object moves from its equilibrium position during a wave or oscillation.

2. How is displacement amplitude measured?

Displacement amplitude is typically measured in meters (m) or centimeters (cm) using a ruler or other measuring device.

3. What are the factors that affect displacement amplitude?

The factors that affect displacement amplitude include the frequency, wavelength, and energy of the wave or oscillation, as well as the properties of the medium through which the wave is traveling.

4. What is the relationship between displacement amplitude and wave intensity?

The displacement amplitude of a wave does not directly affect its intensity. However, a larger displacement amplitude can result in a greater energy transfer, leading to a higher intensity wave.

5. How does displacement amplitude relate to the concept of standing waves?

Displacement amplitude plays a key role in the formation of standing waves. In standing waves, particles at certain points remain at their equilibrium position, while particles at other points experience maximum displacement amplitude.

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