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(II) \(\mathrm{A} .0 .40\) -kg cord is stretched between two supports, 7.8 \(\mathrm{m}\) apart. When one support is struck by a hammer, a transverse wave travels down the cord and reaches the other support in 0.85 \(\mathrm{s}\) . What is the tension in the cord?

Short Answer

Expert verified
The tension in the cord is approximately 4.32 N.

Step by step solution

01

Understand the Problem

We need to find the tension in a cord based on how fast a wave travels along it. We know the wave speed, as it travels 7.8 m in 0.85 s, and the mass of the cord is given as 0.40 kg.
02

Calculate the Wave Speed

First, determine the wave speed using the formula for speed: \( v = \frac{d}{t} \), where \( d = 7.8 \text{ m} \) is the distance and \( t = 0.85 \text{ s} \) is the time. Thus, \( v = \frac{7.8}{0.85} \approx 9.18 \text{ m/s} \).
03

Set up the Wave Speed Formula

The wave speed on a stretched string is given by \( v = \sqrt{\frac{T}{\mu}} \), where \( T \) is the tension in the string, and \( \mu \) is the linear mass density \( \mu = \frac{m}{L} \).
04

Calculate Linear Mass Density

Calculate the linear mass density of the cord \( \mu \) using the formula \( \mu = \frac{m}{L} \), where \( m = 0.40 \text{ kg} \) and \( L = 7.8 \text{ m} \). So, \( \mu = \frac{0.40}{7.8} \approx 0.0513 \text{ kg/m} \).
05

Solve for the Tension in the Cord

Plug the values into the wave speed formula: \( v = \sqrt{\frac{T}{\mu}} \). Rearrange it to solve for \( T \):\[ T = v^2 \times \mu \]Substitute \( v \approx 9.18 \text{ m/s} \) and \( \mu \approx 0.0513 \text{ kg/m} \):\[ T = (9.18)^2 \times 0.0513 \approx 4.32 \text{ N} \]
06

Conclusion

The tension in the cord is approximately 4.32 N.

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Key Concepts

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

Tension Calculation
To calculate the tension in a cord when a wave travels along it, we can use the relationship between wave speed, tension, and linear mass density. A wave's speed on a string, denoted as \(v\), is mathematically related to the tension \(T\) and the linear mass density \(\mu\) of the string via the equation \(v = \sqrt{\frac{T}{\mu}}\). This equation tells us how tightly the string is stretched and how dense it is.To find the tension, rearrange the equation to \(T = v^2 \times \mu\). Here, \(v\) is the wave speed which we can determine by dividing the distance the wave travels by the time it takes. In the given problem, the wave travels 7.8 meters in 0.85 seconds, which calculates to \(v = 9.18 \text{ m/s}\).By understanding this equation, you can compute the tension in any string given the wave speed and linear mass density. This equation is crucial in fields like physics and engineering, where controlling the tension of wires and strings is essential.
Linear Mass Density
Linear mass density, represented by \(\mu\), is a measure of how much mass is distributed along a unit length of a string or cord. It offers insight into how dense or heavy a string is for a given length and is a critical factor when calculating wave speed.To compute the linear mass density, use the formula \(\mu = \frac{m}{L}\), where \(m\) is the total mass of the cord or string, and \(L\) is its total length. This formula helps in breaking down a complex length of mass into simpler terms.- In the exercise, the mass \(m\) given is 0.40 kg.- The length \(L\) of the cord is 7.8 meters.- Therefore, the linear mass density is \(\mu = \frac{0.40}{7.8} \approx 0.0513 \text{ kg/m}\).Understanding linear mass density helps predict how different materials will respond to forces like tension, conveying why it is such a central component in physical wave equations.
Transverse Wave
Transverse waves are types of waves where the motion of the wave medium is perpendicular to the direction of the wave itself. Think of the ripples on a pond or vibrations on a stretched string. They are easy to visualize and can show up in many forms in both natural and constructed settings. Examples of transverse waves include:
  • Vibrations on a guitar string when plucked.
  • Light waves, which are electromagnetic transverse waves.
  • Seismic S-waves that move through the Earth.
In the exercise given, a transverse wave travels across a 7.8-meter cord. When one end of the cord is struck, it creates waves that travel through the cord at a speed determined by the cord’s tension and linear mass density. Examining transverse waves reveals not only the basics of wave motion but also essential properties like velocity and energy, tying together tension and density in the context of wave motion.

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Most popular questions from this chapter

A 10.0 -m-long wire of mass 152 \(\mathrm{g}\) is stretched under a tension of 255 \(\mathrm{N} .\) A pulse is generated at one end, and 20.0 \(\mathrm{ms}\) later a second pulse is generated at the opposite end. Where will the two pulses first meet?

What frequency of sound would have a wavelength the same size as a 1.0 -m-wide window? (The speed of sound is \(344 \mathrm{~m} / \mathrm{s}\) at \(20^{\circ} \mathrm{C} .\) ) What frequencies would diffract through the window?

(II) A small steel wire of diameter 1.0 \(\mathrm{mm}\) is connected to an oscillator and is under a tension of 7.5 \(\mathrm{N}\) . The frequency of the oscillator is 60.0 \(\mathrm{Hz}\) and it is observed that the amplitude of the wave on the steel wire is 0.50 \(\mathrm{cm} .\) (a) What is the power output of the oscillator, assuming that the wave is not reflected back? (b) If the power output stays constant but the frequency is doubled, what is the amplitude of the wave?

(I) An earthquake \(P\) wave traveling \(8.0 \mathrm{~km} / \mathrm{s}\) strikes a boundary within the Earth between two kinds of material. If it approaches the boundary at an incident angle of \(52^{\circ}\) and the angle of refraction is \(31^{\circ}\), what is the speed in the second medium?

(I) Water waves approach an underwater "shelf" where the velocity changes from \(2.8 \mathrm{~m} / \mathrm{s}\) to \(2.5 \mathrm{~m} / \mathrm{s}\). If the incident wave crests make a \(35^{\circ}\) angle with the shelf, what will be the angle of refraction?

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