Math Problem Statement

Період плоскої звукової хвилі дорівнює 5 мс, амплітуда 0,2 мм та довжина хвилі 1,5 м. Для точки середовища, що знаходиться на 5 м від джерела, визначити зміщення, швидкість і прискорення в момент часу t = 10 мс.

Solution

Let's go through this problem step by step.

We are given the following dataLet's go through this problem step by step.

We are given the following

  1. Period of the wave (T): T=5ms=0.005sT = 5 \, \text{ms} = 0.005 \, \text{s}
  2. Amplitude of the wave (A): A=0.2mm=0.0002mA = 0.2 \, \text{mm} = 0.0002 \, \text{m}
  3. Wavelength of the wave (λ): λ=1.5m\lambda = 1.5 \, \text{m}
  4. Position of the point: x=5mx = 5 \, \text{m}
  5. Time: t=10ms=0.01st = 10 \, \text{ms} = 0.01 \, \text{s}

We need to find:

  • Displacement (ξ(x,t)\xi(x, t))
  • Velocity (v(x,t)v(x, t))
  • Acceleration (a(x,t)a(x, t))

Step 1: Angular Frequency and Wave Number

First, we calculate the angular frequency (ω\omega) and wave number (kk).

  1. Angular frequency (ω\omega): ω=2πT=2π0.005=400πrad/s\omega = \frac{2\pi}{T} = \frac{2\pi}{0.005} = 400\pi \, \text{rad/s}

  2. Wave number (kk): k=2πλ=2π1.5=2π1.54.19rad/mk = \frac{2\pi}{\lambda} = \frac{2\pi}{1.5} = \frac{2\pi}{1.5} \approx 4.19 \, \text{rad/m}

Step 2: Displacement Function

The displacement of a point in a wave can be described by: ξ(x,t)=Acos(kxωt)\xi(x, t) = A \cos(kx - \omega t)

For x=5mx = 5 \, \text{m} and t=0.01st = 0.01 \, \text{s}, we substitute the values: ξ(5,0.01)=0.0002cos((4.19)(5)(400π)(0.01))\xi(5, 0.01) = 0.0002 \cos((4.19)(5) - (400\pi)(0.01))

Let's calculate this step-by-step:

  1. Calculate kxkx: 4.19×5=20.954.19 \times 5 = 20.95
  2. Calculate ωt\omega t: 400π×0.0112.57400\pi \times 0.01 \approx 12.57
  3. Substitute these values: ξ(5,0.01)=0.0002cos(20.9512.57)\xi(5, 0.01) = 0.0002 \cos(20.95 - 12.57)

Calculate 20.9512.578.3820.95 - 12.57 \approx 8.38, and then: ξ(5,0.01)=0.0002cos(8.38)0.0002×(0.491)=0.0000982m\xi(5, 0.01) = 0.0002 \cos(8.38) \approx 0.0002 \times (-0.491) = -0.0000982 \, \text{m}

Step 3: Velocity Function

The velocity is the time derivative of displacement: v(x,t)=ξ(x,t)t=Aωsin(kxωt)v(x, t) = \frac{\partial \xi(x, t)}{\partial t} = A \omega \sin(kx - \omega t)

Substitute the values: v(5,0.01)=0.0002×400π×sin(20.9512.57)v(5, 0.01) = 0.0002 \times 400\pi \times \sin(20.95 - 12.57)

Using sin(8.38)0.871\sin(8.38) \approx 0.871: v(5,0.01)0.0002×400π×0.8710.219m/sv(5, 0.01) \approx 0.0002 \times 400\pi \times 0.871 \approx 0.219 \, \text{m/s}

Step 4: Acceleration Function

The acceleration is the time derivative of velocity: a(x,t)=Aω2cos(kxωt)a(x, t) = -A \omega^2 \cos(kx - \omega t)

Substitute the values: a(5,0.01)=0.0002×(400π)2cos(20.9512.57)a(5, 0.01) = -0.0002 \times (400\pi)^2 \cos(20.95 - 12.57)

Using cos(8.38)0.491\cos(8.38) \approx -0.491: a(5,0.01)0.0002×(400π)2×0.49149.6m/s2a(5, 0.01) \approx -0.0002 \times (400\pi)^2 \times -0.491 \approx 49.6 \, \text{m/s}^2

Final Answers

  1. Displacement: ξ(5,0.01)0.0000982m\xi(5, 0.01) \approx -0.0000982 \, \text{m}
  2. Velocity: v(5,0.01)0.219m/sv(5, 0.01) \approx 0.219 \, \text{m/s}
  3. Acceleration: a(5,0.01)49.6m/s2a(5, 0.01) \approx 49.6 \, \text{m/s}^2

Would you like more details on any of these steps?

Here are some related questions for further practice:

  1. How would the results change if the amplitude were doubled?
  2. What effect does increasing the wavelength have on the displacement at a fixed point?
  3. How would the acceleration change if the period of the wave was decreased?
  4. Can you derive the velocity expression from the displacement function for a general sinusoidal wave?
  5. How would you calculate the energy transported by this wave over time?

Tip: Remember, angular frequency ω\omega and wave number kk are essential in determining the behavior of waves in sinusoidal wave functions.

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Math Problem Analysis

Mathematical Concepts

Wave Motion
Harmonic Motion
Trigonometric Functions

Formulas

Displacement formula: ξ(x, t) = A cos(kx - ωt)
Velocity formula: v(x, t) = Aω sin(kx - ωt)
Acceleration formula: a(x, t) = -Aω^2 cos(kx - ωt)
Angular frequency: ω = 2π / T
Wave number: k = 2π / λ

Theorems

Wave equation
Trigonometric identities

Suitable Grade Level

Undergraduate Physics