/*! 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 80 A breadbox is made to move along... [FREE SOLUTION] | 91Ó°ÊÓ

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A breadbox is made to move along an \(x\) axis from \(x=0.15 \mathrm{~m}\) to \(x=1.20 \mathrm{~m}\) by a force with a magnitude given by \(F=\exp \left(-2 x^{2}\right),\) with \(x\) in meters and \(F\) in newtons. (Here exp is the exponential function.) How much work is done on the breadbox by the force?

Short Answer

Expert verified
The work done on the breadbox is approximately 0.52 Joules.

Step by step solution

01

Understand Work Formula

The work done by a force when moving an object along a path is given by the integral of the force with respect to distance. The formula is: \\[\text{Work} = \int_{a}^{b} F(x) \, dx\] \where \(a\) and \(b\) are the initial and final positions.
02

Set Up the Integral

In this problem, the force applied on the breadbox is given by \(F(x) = \exp(-2x^2)\). The breadbox moves from \(x = 0.15 \, \text{m}\) to \(x = 1.20 \, \text{m}\). So we need to calculate: \\[\int_{0.15}^{1.20} \exp(-2x^2) \, dx\]
03

Solve the Integral

The integral of \(\exp(-2x^2)\) with respect to \(x\) is not a standard elementary function. It involves the error function (erf). The result is: \\[\left[ \frac{1}{2} \sqrt{\frac{\pi}{2}} \, \text{erf}(\sqrt{2}x) \right]_{0.15}^{1.20}\]
04

Calculate Error Function Values

Use a calculator or a table to find the approximate values of the error function: \- For \(x = 1.20\), \(\text{erf}(\sqrt{2} \times 1.20) \approx 0.99759\) \- For \(x = 0.15\), \(\text{erf}(\sqrt{2} \times 0.15) \approx 0.16601\)
05

Substitute and Finalize Work

Substitute the erf values into the work formula: \\[\text{Work} = \frac{1}{2} \sqrt{\frac{\pi}{2}} \left(0.99759 - 0.16601\right)\] \Calculate this to find the total work done.
06

Compute Numerical Result

\[\text{Work} = \frac{1}{2} \times 1.25331 \times (0.99759 - 0.16601) \approx 0.519530 \, \text{Joules}\] \So, the work done by the force on the breadbox is approximately 0.52 Joules.

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Key Concepts

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

Integral Calculus
Integral calculus is a fundamental concept in mathematics used to find the area under a curve, which in physics is often applied to calculate work done by a force. When dealing with moving objects, work can be determined by integrating the force over a distance. This means you take the infinitesimal contributions of the force at each small distance and sum them up over the moving path.

In our exercise, the force exerted on the breadbox is described by a function that varies with the position, denoted as \(F(x) = \exp(-2x^2)\). By integrating this force function from the initial position \(x=0.15\) meters to the final position \(x=1.20\) meters, we can find the total work done on the object.

The integral to be solved is written as follows:
  • \[ \text{Work} = \int_{0.15}^{1.20} \exp(-2x^2) \, dx \]
This involves evaluating the force function through the defined bounds, fully capturing how the force contributes to work at each incremental step along the path.
Exponential Function
The exponential function is a mathematical function characterized by expressions such as \(e^x\) or \(a^x\), where \(e\) is Euler's number (approximately 2.71828). It is a unique function in that it grows (or decays) exponentially - meaning the rate of change is proportional to the value of the function itself.

In the context of this problem, the force function is given as \(F(x) = \exp(-2x^2)\). The expression \(\exp(-2x^2)\) follows an exponential decay pattern, which indicates that as the position \(x\) increases, the force exerted decreases rapidly. This behavior is typical of exponential functions, especially when dealing with negative exponents which contribute to the decay.

Understanding how the exponential function behaves is crucial to understanding the nature of the force applied on the breadbox as it moves along the \(x\)-axis. The force decreases with increasing \(x\), dramatically affecting the work calculated over the specified distance.
Error Function (erf)
The error function, commonly denoted as \(\text{erf}(x)\), is a special function that arises in the field of probability, statistics, and partial differential equations. It is related to the Gaussian distribution, commonly known as the "normal" distribution, and appears when dealing with integrals of exponential functions like \(e^{-x^2}\).

In this specific problem, the work calculation requires integrating \(\exp(-2x^2)\). This integral doesn't resolve into a simple elementary function. Instead, it involves the error function due to its relation to the Gaussian integral. The integral part of the step-by-step solution results in:
  • \[ \left[ \frac{1}{2} \sqrt{\frac{\pi}{2}} \, \text{erf}(\sqrt{2}x) \right]_{0.15}^{1.20} \]
The values of the error function at specified points \(x = 1.20\) and \(x = 0.15\) are needed to finalize the result. Utilizing tables or calculators to find these values bridges the gap to calculating the total work done accurately. The error function thus helps to quantify the extent of work executed by the exponentially behaving force on the moving breadbox.

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Most popular questions from this chapter

If a car of mass \(1200 \mathrm{~kg}\) is moving along a highway at \(120 \mathrm{~km} / \mathrm{h}\) what is the car's kinetic energy as determined by someone standing alongside the highway?

An iceboat is at rest on a frictionless frozen lake when a sudden wind exerts a constant force of \(200 \mathrm{~N},\) toward the east, on the boat. Due to the angle of the sail, the wind causes the boat to slide in a straight line for a distance of \(8.0 \mathrm{~m}\) in a direction \(20^{\circ}\) north of east. What is the kinetic energy of the iceboat at the end of that \(8.0 \mathrm{~m} ?\)

If a Saturn \(\mathrm{V}\) rocket with an Apollo spacecraft attached had a combined mass of \(2.9 \times 10^{5} \mathrm{~kg}\) and reached a speed of \(11.2 \mathrm{~km} / \mathrm{s}\), how much kinetic energy would it then have?

If a ski lift raises 100 passengers averaging \(660 \mathrm{~N}\) in weight to a height of \(150 \mathrm{~m}\) in \(60.0 \mathrm{~s}\), at constant speed, what average power is required of the force making the lift?

A \(250 \mathrm{~g}\) block is dropped onto a relaxed vertical spring that has a spring constant of \(k=\) \(2.5 \mathrm{~N} / \mathrm{cm}\) (Fig. \(7-46)\). The block becomes attached to the spring and compresses the spring \(12 \mathrm{~cm}\) before momentarily stopping. While the spring is being compressed, what work is done on the block by (a) the gravitational force on it and (b) the spring force? (c) What is the speed of the block just before it hits the spring? (Assume that friction is negligible.) (d) If the speed at impact is doubled, what is the maximum compression of the spring?

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