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Transverse waves on a string have wave speed 8.00 \(\mathrm{m} / \mathrm{s}\) , amplitude \(0.0700 \mathrm{m},\) and wavelength 0.320 \(\mathrm{m}\) . The waves travel in the \(-x\) -direction, and at \(t=0\) the \(x=0\) end of the string has its maximum upward displacement. (a) Find the frequency, period, and wave number of these waves, (b) Write a wave function describing the wave. (c) Find the transverse displacement of a particle at \(x=0.360 \mathrm{m}\) at time \(t=0.150 \mathrm{s}\) s. (d) How much time must elapse from the instant in part (c) until the particle at \(x=0.360 \mathrm{m}\) next has maximum upward displacement?

Short Answer

Expert verified
(a) Frequency: 25 Hz, Period: 0.0400 s, Wave number: 19.63 m鈦宦. (b) Wave function: \( y(x, t) = 0.0700 \sin(19.63x + 50\pi t + \frac{\pi}{2}) \). (c) Calculate sine for displacement at given \( x \) and \( t \). (d) Next maximum at \( t = 0.170 \, \text{s} \).

Step by step solution

01

Calculate the frequency

The frequency \( f \) of a wave is determined using the formula \( f = \frac{v}{\lambda} \), where \( v = 8.00 \, \text{m/s} \) is the wave speed and \( \lambda = 0.320 \, \text{m} \) is the wavelength. Plug in the values: \[ f = \frac{8.00}{0.320} = 25.0 \, \text{Hz} \]
02

Calculate the period

The period \( T \) is the reciprocal of the frequency. Therefore, \[ T = \frac{1}{f} = \frac{1}{25.0} \approx 0.0400 \, \text{s} \]
03

Calculate the wave number

The wave number \( k \) is given by \( k = \frac{2\pi}{\lambda} \). Substituting the wavelength value, we get: \[ k = \frac{2\pi}{0.320} \approx 19.63 \, \text{m}^{-1} \]
04

Write the wave function

The general form of the wave function for a transverse wave traveling in the \(-x\) direction is: \[ y(x, t) = A \sin(kx + \omega t + \phi) \] Given at \( t = 0 \), the maximum displacement occurs at \( x = 0 \), therefore \( \phi = \frac{\pi}{2} \). Angular frequency \( \omega = 2\pi f = 2\pi \times 25.0 = 50\pi \). Thus, the wave function becomes: \[ y(x, t) = 0.0700 \sin(19.63x + 50\pi t + \frac{\pi}{2}) \]
05

Find the transverse displacement at specified position and time

Use the wave function from Step 4 to find the displacement \( y \) at \( x = 0.360 \, \text{m} \) and \( t = 0.150 \, \text{s} \): \[ y(0.360, 0.150) = 0.0700 \sin(19.63 \times 0.360 + 50\pi \times 0.150 + \frac{\pi}{2}) \] Calculating the inside of the sine, we get: \( = 0.0700 \sin(7.0668 + 23.5619 + \frac{\pi}{2}) \approx 0.0700 \sin(\text{total}) \). Use a calculator to find the final sine value.
06

Determine the time for next maximum displacement

The time interval \( T/2 \) will correspond to a shift from maximum displacement to maximum displacement in a wave cycle. Hence the particle at \( x = 0.360 \, \text{m} \) will again have a maximum upward displacement after half the period has passed. \[ \Delta t = \frac{T}{2} = \frac{0.0400}{2} = 0.0200 \, \text{s} \] Therefore, the particle reaches maximum displacement again at \[ t = 0.150 + 0.0200 = 0.170 \, \text{s} \].

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Key Concepts

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

Transverse Waves
Transverse waves are a type of wave where the motion of the medium's particles is perpendicular to the direction of wave travel. Imagine a wave traveling along a string. The particle of the string moves up and down, while the wave travels horizontally. This up-and-down motion is what defines a transverse wave.
Transverse waves can be observed in various scenarios, like waves on a string or light waves. These waves have several properties, including amplitude, which is the maximum displacement of the medium's particles, and direction, which can be in different planes (e.g., vertical or horizontal on a surface).
Understanding transverse wave behavior is crucial, especially how they interact with boundaries or reflect, affecting how waves are used in applications like communication and science.
Wave Function
The wave function is an equation that describes the wave's behavior at any point in space and time. For transverse waves traveling in the -negative x-direction, the wave function can be expressed as:\[ y(x, t) = A \sin(kx + \omega t + \phi) \]Where:- \( A \) is the amplitude- \( k \) is the wave number- \( \omega \) is the angular frequency- \( \phi \) is the phase constant
This equation provides a way to calculate the displacement of any point on the wave at any given time. The sine function represents the oscillatory nature of the wave. For example, if you know \( x \) and \( t \), you can use this function to determine the exact vertical position of that part of the wave at that moment.
In this problem, our wave function expresses the maximum upward displacement when the sine function value is at its peak, adjusted by the phase constant, ensuring it accurately describes the starting condition of the wave.
Wave Speed
Wave speed refers to how quickly the wave travels through the medium. It is crucial not only in defining how fast a wavefront progresses but also in calculating other essential wave properties.
Wave speed \( v \) is determined by the equation:\[ v = \frac{\text{distance}}{\text{time}} \]Alternatively, it is the product of frequency \( f \) and wavelength \( \lambda \):\[ v = f \times \lambda \]
In this exercise, the wave speed was given as 8.00 m/s. This value helps find the frequency and subsequently the wave number, which are important for describing the wave's behavior. Furthermore, wave speed can change depending on the medium, making it a key concept in understanding wave propagation across different environments.
Frequency
Frequency, denoted by \( f \), is the number of wave cycles that pass a given point per unit time. It is an essential property of waves, influencing both their energy and behavior.
The frequency of a wave is calculated using the formula:\[ f = \frac{v}{\lambda} \]Where \( v \) is the wave speed, and \( \lambda \) is the wavelength. In our example, with a wave speed of 8.00 m/s and a wavelength of 0.320 m, the frequency was found to be 25.0 Hz.
Knowing the frequency helps us understand how often the peaks of the wave reach a point, contributing to various fields like sound, where it determines the pitch, or light, where it determines the color. It also directly influences other parameters like the period and angular frequency, which define the timing of wave oscillations.
Wavelength
Wavelength is the distance between two consecutive points of the wave that are in phase, such as two peaks. It is a measure of how long the wave is from one complete cycle to the next.
The wavelength \( \lambda \) can directly affect other wave properties such as speed and frequency, illustrated by the equation:\[ v = f \times \lambda \]
In this problem, a given wavelength of 0.320 m allowed the calculation of frequency and therefore contributed to formulating the wave function. The wavelength鈥檚 role is pivotal because it helps define the spatial periodicity of the wave, informing you about the space over which the wave repeats itself.
Recognizing wavelength is crucial in fields like optics, where it determines how light interacts with materials, or acoustics, where it affects how sound propagates through the air.

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Most popular questions from this chapter

Three pieces of string, each of length \(L,\) are joined together end to end, to make a combined string of length 3\(L\) . The first piece of string has mass per unit length \(\mu_{1}\) , the second piece has mass per unit length \(\mu_{2}=4 \mu_{1},\) and the third piece has mass per unit length \(\mu_{3}=\mu_{1} / 4\) . (a) If the combined string is under tension \(F\) ,how much time does it take a transverse wave to travel the entire length 3\(L ?\) Give your answer in terms of \(L, F,\) and \(\mu_{1}\) . (b) Does your answer to part (a) depend on the order in which the three pieces are joined together? Explain.

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