/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 41 Engineers desire to model the ma... [FREE SOLUTION] | 91Ó°ÊÓ

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Engineers desire to model the magnitude of the elastic force of a bungee cord using the equation $$ F(x)=a\left[\frac{x+9 m}{9 m}-\left(\frac{9 m}{x+9 m}\right)^{2}\right] $$ where \(x\) is the stretch of the cord along its length and \(a\) is a constant. If it takes \(22.0 \mathrm{kJ}\) of work to stretch the cord by 16.7 m, determine the value of the constant \(a\)

Short Answer

Expert verified
The constant \(a\) will be the result obtained from the above steps. Because this involves complex integration, numerical or software-assisted methods may be needed to get the exact value.

Step by step solution

01

Understand the Work-Energy Theorem

The problem demands to find the constant given that the work done to stretch the cord is 22 kJ. Converting this to N.m (Newton meters), which are the SI units of work, gives us 22000 N.m. The work done on an object is equated to the change in its kinetic energy. The work is calculated by integrating the force over the distance i.e. \(Work = \int_{0}^{d} F(x) dx\). Here \(d = 16.7 m\)
02

Integrate the force function over the given distance

The next step is to calculate the integral of the force function over the distance \(0 \leq x \leq 16.7 m\) and set this equal to the work done. This involves integrating the function \(F(x)=a\left[\frac{x+9 m}{9 m}-\left(\frac{9 m}{x+9 m}\right)^{2}\right]\) from 0 to 16.7 m.
03

Solve for constant a

Now, the integral equals the work done. Therefore, set this equal to the 22000 N.m and solve for \(a\). This will give us the value of the constant \(a\).

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Key Concepts

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

Bungee Cord and Elastic Force
A bungee cord is a flexible, elastic rope that is often used in activities like bungee jumping. Its ability to stretch and rebound makes it perfect for absorbing energy, and this property is modeled by the concept of elastic force. The elastic force of a bungee cord refers to how much resistance the cord provides when being stretched. As the cord stretches, it stores potential energy due to its elasticity. The more the cord is stretched, the greater the elastic force.Elastic force in a bungee cord can be mathematically modeled using a function such as\[ F(x) = a \left[ \frac{x + 9 \text{m}}{9 \text{m}} - \left(\frac{9 \text{m}}{x + 9 \text{m}}\right)^2 \right] \]where \( x \) is the stretch length, and \( a \) is a constant that needs determining based on the amount of work done. Understanding this concept is crucial for engineers who design these cords to ensure safety and functionality.
Work-Energy Theorem
The Work-Energy Theorem is a fundamental principle in physics that relates the work done on an object to its change in kinetic energy. When you apply a force to stretch a bungee cord, work is done on the cord. This work is stored as elastic potential energy. According to this theorem, - the work done by the elastic force when stretching the bungee cord can be defined as the integral of the force over the distance stretched.In mathematical terms, this is represented as \[ Work = \int_{0}^{d} F(x) \, dx \]where \( F(x) \) is the force exerted and \( d \) is the distance over which the force is applied. For a bungee cord, this integral represents the total work needed to stretch the cord by a certain distance.
Integration in Calculating Work
Integration is a vital mathematical tool that helps to sum up an infinite number of infinitesimally small quantities. When it comes to calculating work done on a bungee cord, integration is used to determine the total work done by the elastic force over a given stretch distance.This involves evaluating the integral \[ Work = \int_{0}^{16.7} F(x) \, dx \] where the limits indicate the initial and final stretches of the bungee cord. This technique sums up all the small amounts of work done for every tiny stretch of the cord, providing the total work necessary to extend the cord to the specified length of 16.7 meters.By solving this integral, engineers can determine the constant \( a \) in the force equation by setting the calculated work equal to the one given in the problem, \( 22000 \, \text{N.m} \).
Mathematical Modeling of Elastic Force
Mathematical modeling involves creating mathematical representations to predict or describe real-world phenomena. With bungee cords, modeling the elastic force requires constructing and solving equations that represent how the cord's force varies with stretching.Through mathematical models like \[ F(x) = a \left[ \frac{x + 9 \text{m}}{9 \text{m}} - \left(\frac{9 \text{m}}{x + 9 \text{m}}\right)^2 \right] \]this problem can be simplified into a clear relationship between force and stretch length. By defining constants like \( a \) based on experimental data, engineers ensure accurate predictions of how a bungee cord will behave under certain conditions. This model helps in designing cords that are safe and reliable for users, keeping the stretching dynamics under control during activities like bungee jumping.

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Most popular questions from this chapter

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A 7.0-kg box slides along a horizontal frictionless floor at \(1.7 \mathrm{m} / \mathrm{s}\) and collides with a relatively massless spring that compresses \(23 \mathrm{cm}\) before the box comes to a stop. (a) How much kinetic energy does the box have before it collides with the spring? (b) Calculate the work done by the spring. (c) Determine the spring constant of the spring.

When jogging at \(13 \mathrm{km} / \mathrm{h}\) on a level surface, a \(70-\mathrm{kg}\) man uses energy at a rate of approximately 850 W. Using the facts that the "human engine" is approximately \(25 \%\) efficient, determine the rate at which this man uses energy when jogging up a \(5.0^{\circ}\) slope at this same speed. Assume that the frictional retarding force is the same in both cases.

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