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A horizontal wire is stretched with a tension of 94.0 N, and the speed of transverse waves for the wire is 406 m/s. What must the amplitude of a traveling wave of frequency 69.0 Hz be for the average power carried by the wave to be 0.365 W?

Short Answer

Expert verified
The amplitude is approximately 0.178 mm.

Step by step solution

01

Identify given values

The tension in the wire, \( T = 94.0 \, \text{N} \), the wave speed, \( v = 406 \, \text{m/s} \), the frequency, \( f = 69.0 \, \text{Hz} \), and the average power, \( P = 0.365 \, \text{W} \), are given.
02

Calculate the linear mass density

The mass per unit length (linear mass density), \( \mu \), can be calculated using the tension \( T \) and wave speed \( v \) with the formula: \( v = \sqrt{\frac{T}{\mu}} \). Rearrange to find \( \mu = \frac{T}{v^2} \). Substitute the given values: \( \mu = \frac{94.0}{406^2} \, \text{kg/m} \).
03

Use the power equation

The average power for a wave is given by the formula \( P = \frac{1}{2} \mu v (2\pi f)^2 A^2 \). We need to find the amplitude \( A \).
04

Rearrange for amplitude

Rearrange the power equation to solve for amplitude \( A \): \( A = \sqrt{\frac{2P}{\mu v (2\pi f)^2}} \). Substitute the known values of \( P \), \( \mu \), \( v \), and \( f \).
05

Perform the calculation

Substitute \( P = 0.365 \), \( \mu = \frac{94.0}{406^2} \), \( v = 406 \), and \( f = 69.0 \) into the amplitude formula. Calculate to get \( A \approx 1.78 \times 10^{-4} \text{m} \) (or 0.178 mm).

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Key Concepts

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

Amplitude
Amplitude refers to the maximum extent of a vibration or displacement from the rest position in a wave. In wave mechanics, amplitude plays a crucial role in determining the energy carried by a wave. A larger amplitude means that the wave carries more energy. When discussing traveling waves on a wire, understanding how amplitude influences power is vital.
In the context of wave energy, the power carried by the wave is proportional to the square of the amplitude. This means that even a small increase in amplitude can significantly increase the energy carried by the wave.
  • In the formula for wave power, amplitude (\(A\)) appears squared, indicating its importance in determining wave energy.
  • The power formula used is \( P = \frac{1}{2} \mu v (2\pi f)^2 A^2 \), where \(P\) is power, \(\mu\) is linear mass density, \(v\) is velocity, and \(f\) is frequency.
  • Thus, solving for amplitude involves rearranging the power formula appropriately.
To find the amplitude when other parameters like tension and wave speed are provided, it is essential to rearrange this power equation. Then, plug in the known values to calculate the required amplitude for a specific energy output.
Tension in a Wire
The tension in a wire is a key factor that influences the behavior and properties of waves traveling through the wire. In physics, tension refers to the force that is applied along the length of the wire to stretch it. This tension determines the speed at which waves propagate through the wire.
The speed of transverse waves in a stretched wire is given by the equation \( v = \sqrt{\frac{T}{\mu}} \), where \(v\) is the speed of the wave, \(T\) is the tension in the wire, and \(\mu\) is the linear mass density. The relationship shows how tension in a wire impacts wave speed directly:
  • Greater tension increases wave speed as the wire becomes stiffer, allowing waves to travel faster.
  • Lower tension reduces wave speed, as the wire is less stiff and waves travel slower.
By understanding how tension affects wave speed, one can effectively control the characteristics of waves in a wire. For example, musicians manipulate tension to tune string instruments to desired frequencies.
Linear Mass Density
Linear mass density, denoted by \(\mu\), is the mass per unit length of a wire or string. It is a critical factor in determining wave speed and behavior along the wire. To find linear mass density, use the formula \( \mu = \frac{T}{v^2} \), where \(T\) is the tension and \(v\) is the wave speed.
This equation highlights the inverse relationship between linear mass density and wave speed. A greater mass density implies that waves travel slower:
  • If the wire is heavier per unit of length, it takes more force to move it, resulting in slower wave propagation.
  • Conversely, a lighter wire allows for quicker wave travel, given the same applied tension.
Understanding linear mass density is crucial for applications involving wave mechanics, such as designing musical instruments or engineering systems involving vibrations and waves.
Transverse Waves
Transverse waves are a type of wave where the motion of the medium's particles is perpendicular to the direction of the wave's travel. These waves are common in many physical contexts and can occur in strings, water, and even light.
Unlike longitudinal waves, where motion is parallel, transverse waves involve motion that is side-to-side or up-and-down relative to the wave's direction of travel.
  • In wires, transverse waves consist of periodic oscillations that move through the wire, driven by external forces such as tension.
  • This perpendicular motion of the medium's particles distinguishes transverse waves from other wave types.
  • They are also characterized by features like amplitude, wavelength, frequency, and wave speed.
Transverse waves are vital in understanding complex wave phenomena and are applicable in numerous fields, including acoustics, optics, and electromagnetic theory. Recognizing their properties is key to mastering wave mechanics and related scientific disciplines.

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Most popular questions from this chapter

A jet plane at takeoff can produce sound of intensity 10.0 W/m\(^2\) at 30.0 m away. But you prefer the tranquil sound of normal conversation, which is 1.0 \(\mu\)W/m\(^2\). Assume that the plane behaves like a point source of sound. (a) What is the closest distance you should live from the airport runway to preserve your peace of mind? (b) What intensity from the jet does your friend experience if she lives twice as far from the runway as you do? (c) What power of sound does the jet produce at takeoff?

With what tension must a rope with length 2.50 m and mass 0.120 kg be stretched for transverse waves of frequency 40.0 Hz to have a wavelength of 0.750 m?

Transverse waves on a string have wave speed 8.00 m/s, amplitude 0.0700 m, and wavelength 0.320 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 \(x = 0.360\) m at time \(t = 0.150\) s. (d) How much time must elapse from the instant in part (c) until the particle at \(x = 0.360\) m next has maximum upward displacement?

A transverse wave on a rope is given by $$y(x, t) = (0.750 \, \mathrm{cm}) \mathrm{cos} \space \pi[(10.400 \, \mathrm{cm}^{-1})x + (250 \mathrm s^{-1})t]$$ (a) Find the amplitude, period, frequency, wavelength, and speed of propagation. (b) Sketch the shape of the rope at these values of \(t:\) 0, 0.0005 s, 0.0010 s. (c) Is the wave traveling in the \(+x-\) or \(-x\)-direction? (d) The mass per unit length of the rope is 0.0500 kg/m. Find the tension. (e) Find the average power of this wave.

(a) A horizontal string tied at both ends is vibrating in its fundamental mode. The traveling waves have speed \(v\), frequency \(f\), amplitude \(A\), and wavelength \(\lambda\). Calculate the maximum transverse velocity and maximum transverse acceleration of points located at (i) \(x = \lambda/2\), (ii) \(x = \lambda /4\), and (iii) \(x = \lambda /8\), from the left-hand end of the string. (b) At each of the points in part (a), what is the amplitude of the motion? (c) At each of the points in part (a), how much time does it take the string to go from its largest upward displacement to its largest downward displacement?

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