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CE Suppose you would like to double the speed of a wave on a string. By what multiplicative factor must you increase the tension?

Short Answer

Expert verified
Increase the tension by a factor of 4 to double the wave speed.

Step by step solution

01

Understand the Relationship Between Wave Speed and Tension

The speed of a wave on a string, denoted as \( v \), is given by the formula \( v = \sqrt{\frac{T}{\mu}} \), where \( T \) represents the tension in the string and \( \mu \) is the linear mass density. This relationship shows that the wave speed is affected by the square root of the tension.
02

Identify the Target Wave Speed

We want to double the current wave speed. If the initial wave speed is \( v \), the target wave speed \( v' \) becomes \( 2v \).
03

Express the New Tension in Terms of the Target Wave Speed

Substitute the desired wave speed into the wave speed formula: \( 2v = \sqrt{\frac{T'}{\mu}} \), where \( T' \) is the new tension. Square both sides to remove the square root: \( 4v^2 = \frac{T'}{\mu} \).
04

Relate the Original and New Tension

From the original wave speed formula, \( v^2 = \frac{T}{\mu} \). Substitute this into the equation from Step 3: \( 4v^2 = 4\frac{T}{\mu} \), so \( 4\frac{T}{\mu} = \frac{T'}{\mu} \).
05

Solve for the Multiplicative Factor of Tension Increase

With \( 4\frac{T}{\mu} = \frac{T'}{\mu} \), simplify to find the relationship between \( T' \) and \( T \): \( T' = 4T \). Therefore, the tension must be increased by a factor of 4.

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Key Concepts

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

Understanding the Tension in a String
In wave mechanics, tension in a string is crucial for determining the behavior of waves traveling along it. Tension refers to the force exerted along the string's length, and this force plays a direct role in how fast waves can move. The greater the tension, the faster the wave can travel. To calculate wave speed, we use the formula: \[ v = \sqrt{\frac{T}{\mu}} \] Here, \( T \) represents the tension in the string, and \( \mu \) is the linear mass density of the string (more on that soon).
  • Higher tension increases wave speed, making waves move faster along the string.
  • Lower tension results in slower wave speeds, as the string isn't "as tight" to carry the wave quickly.
Understanding how to manipulate tension allows us to control wave speed. For example, if you want the wave to move twice as fast, you must increase the tension by a factor of four, as shown in the original solution.
Linear Mass Density Explained
Linear mass density, denoted as \( \mu \), measures how much mass is distributed along a unit length of the string. Think of it as the "thickness" of the string in terms of mass. A heavier, thicker string will naturally have a greater linear mass density, impacting wave propagation. The relationship between wave speed, tension, and linear mass density is expressed in the formula: \[ v = \sqrt{\frac{T}{\mu}} \] From this equation, we understand:
  • If \( \mu \) increases (making the string heavier), wave speed decreases for a given tension.
  • Conversely, decreasing \( \mu \) (using a lighter string) allows waves to travel faster with the same tension.
By adjusting the properties of \( \mu \), we can affect the wave behavior, yet it usually remains constant for a specific string. Therefore, manipulating tension is often more practical for adjusting wave speed.
Get to Know Wave Mechanics
Wave mechanics involves understanding how waves of different types propagate and interact with media, like strings. A key focus is determining how various factors like tension and mass density affect wave speed and behavior. An essential formula in wave mechanics for string waves is: \[ v = \sqrt{\frac{T}{\mu}} \] Here are a few foundational concepts:
  • Medium properties: How waves travel depends on the medium's properties, including tension and linear mass density in strings.
  • Wave types: Waves on strings are typically transverse, meaning disturbances move perpendicular to the wave direction.
  • Energy transfer: Waves carry energy, and understanding their speed is crucial for predicting how vibrations and signals are transmitted.
Wave mechanics encompasses these ideas, focusing on how to modify and predict wave behaviors through physical variables like tension and mass density, as explored in exercises like the one we've seen.

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Most popular questions from this chapter

A steel guitar string has a tension \(T\), length \(L\), and diameter D. Give the multiplicative factor by which the fundamental frequency of the string changes under the following conditions: (a) The tension in the string is increased by a factor of 4 The diameter is \(D\) and the length is \(L\). (b) The diameter of the string is increased by a factor of \(3 .\) The tension is \(T\) and the length is \(L\). (c) The length of the string is halved. The tension is \(T\) and the diameter is \(D\).

IP Twenty violins playing simultaneously with the same intensity combine to give an intensity level of \(82.5 \mathrm{dB}\). (a) What is the intensity level of each violin? (b) If the number of violins is increased to \(40,\) will the combined intensity level be more than, less than, or equal to 165 dB? Explain.

A Slinky has a mass of 0.28 kg and negligible length. When it is stretched \(1.5 \mathrm{m},\) it is found that transverse waves travel the length of the Slinky in \(0.75 \mathrm{s}\). (a) What is the force constant, \(k\), of the Slinky? (b) If the Slinky is stretched farther, will the time required for a wave to travel the length of the Slinky increase, decrease, or stay the same? Explain. (c) If the Slinky is stretched \(3.0 \mathrm{m},\) how much time does it take a wave to travel the length of the Slinky? (The Slinky stretches like an ideal spring, and propagates transverse waves like a rope with variable tension.)

A string \(1.5 \mathrm{m}\) long with a mass of \(2.6 \mathrm{g}\) is stretched between two fixed points with a tension of \(93 \mathrm{N}\). Find the frequency of the fundamental on this string.

A brother and sister try to communicate with a string tied between two tin cans (Figure \(14-33\) ). If the string is \(9.5 \mathrm{m}\) long, has a mass of \(32 \mathrm{g}\), and is pulled taut with a tension of \(8.6 \mathrm{N}\), how much time does it take for a wave to travel from one end of the string to the other?

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