Chapter 17: Problem 2
A wave is described by the equation \(y=(1.0 \mathrm{~mm}) \sin \pi\left(\frac{x}{2.0 \mathrm{~cm}}-\frac{t}{0.01 \mathrm{~s}}\right)\). (a) Find time period and wavelength. (b) Find the speed of particle at \(x=1.0 \mathrm{~cm}\) and time \(t=0.01 \mathrm{~s}\). (c) What are the speeds of the particles at \(x=3.0 \mathrm{~cm}, 5.0 \mathrm{~cm}\) and \(7.0 \mathrm{~cm}\) at \(t=0.01 \mathrm{~s}\) ? (d) What are the speeds of the particles at \(x=1.0 \mathrm{~cm}\) at \(t=0.011,0.012\) and \(0.013 \mathrm{~s}\) ?
Short Answer
Step by step solution
Identify the Given Wave Equation
Calculate the Time Period
Determine the Wavelength
Calculate Speed of the Wave
Velocity of Particle at x=1.0 cm, t=0.01 s
Speed of Particles at Different Positions at t=0.01 s
Speed of the Particle at x=1.0 cm at Different Times
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Angular Frequency
In mathematical terms, angular frequency is given by the equation \( \omega = 2\pi f \), where \( f \) is the frequency of the wave in Hertz (Hz).
Using the provided wave equation, we found \( \omega \) as \( \frac{\pi}{0.01 \text{ s}} \), which was computed from the term \(-\frac{t}{0.01 \text{ s}}\). This represents the angular motion of the wave.
- Angular frequency helps characterize the wave's motion.
- It links together time, frequency, and oscillation.
- Provides insight into the speed of rotation in wave motion.
Wavelength
From our exercise, we derived wavelength using the equation \( k = \frac{2\pi}{\lambda} \), where \( k \) is the wave number. By rearranging, we found that \( \lambda = \frac{2\pi}{k} \). For our specific wave, the wavelength was calculated to be \( 4.0 \text{ cm} \) by solving \( \lambda = \frac{2\pi}{\pi/2.0 \text{ cm}} \).
- Wavelength helps determine wave speed using \( v = f\lambda \).
- Provides spatial perspective of a wave pattern.
- Connects physical space and mathematical descriptions of waves.
Particle Velocity
In our wave equation, particle velocity \( v_p \) was determined by taking the time derivative \( \frac{dy}{dt} \). This led us to the expression \( v_p = -A\omega \cos(kx - \omega t) \). For instance, at \( x = 1.0 \text{ cm} \) and \( t = 0.01 \text{ s} \), the particle velocity is \( 0 \text{ cm/s} \), indicating the point is at rest momentarily.
- Particle velocity marks points of maximum and minimum displacement.
- Aids in understanding kinetic energy at specific points.
- Offers insight into how media particles interact with the wave.
Wave Speed
In our findings, the wave speed was calculated using the formula \( v = f\lambda \). With a frequency \( f = 50 \text{ Hz} \) and a wavelength \( \lambda = 4.0 \text{ cm} \), we determined that \( v = 2 \text{ m/s} \).
- Wave speed ties together wavelength and frequency directly.
- Predicts how quickly wave crests move across space.
- Indicates the energy transmission speed in the wave.