Chapter 5: Problem 13
Find the volume generated by rotating the area bounded by the graphs of each set of equations around the \(x\) -axis. $$ y=x^{2}, x=0, x=2 $$
Short Answer
Expert verified
The volume is \( \frac{32\pi}{5} \).
Step by step solution
01
Understand the Problem
We need to find the volume of the solid formed by rotating the region bounded by the curves \( y = x^2 \), \( x = 0 \), and \( x = 2 \) around the \( x \)-axis.
02
Set Up the Integral
The formula for the volume of a solid of revolution around the \( x \)-axis is \( V = \pi \int_{a}^{b} [f(x)]^2 \, dx \). Here \( f(x) = x^2 \), \( a = 0 \), and \( b = 2 \), so the integral becomes \( V = \pi \int_{0}^{2} (x^2)^2 \, dx = \pi \int_{0}^{2} x^4 \, dx \).
03
Compute the Integral
Calculate the integral \( \int_{0}^{2} x^4 \, dx \). Find the antiderivative: \( \int x^4 \, dx = \frac{x^5}{5} + C \). Now evaluate from 0 to 2: \[ \left. \frac{x^5}{5} \right|_0^2 = \frac{2^5}{5} - \frac{0^5}{5} = \frac{32}{5} \].
04
Calculate the Volume
Substitute the result of the integral back into the formula: \( V = \pi \times \frac{32}{5} = \frac{32\pi}{5} \). This is the volume of the solid obtained by rotating the region around the \( x \)-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Volume of Revolution
When we talk about finding the volume of a solid of revolution, we're referring to a process where a 2D region is spun around an axis to create a 3D object. This is a common technique in calculus to measure the volume of irregular shapes. Let's break it down a bit:
- First, identify the region to be rotated. In this case, the region is bounded by the graph of the function, such as \( y = x^2 \), within certain limits (here, \( x=0 \) to \( x=2 \)).
- This region is rotated about an axis (the \( x \)-axis in our example), sweeping out a volume.
- The shape formed by this rotation is similar to a series of infinitely thin disks or washers stacked together.
Definite Integral
The definite integral is a key tool used in calculus to compute areas, volumes, and more. Essentially, the definite integral calculates the accumulated sum of quantities, such as area under a curve or in our case, volume of a solid of revolution. Here’s a simplified breakdown:
- Definition: A definite integral from \(a\) to \(b\) is represented as \( \int_{a}^{b} f(x) \, dx \) and measures the net area under the curve of \(f(x)\) from \(x = a\) to \(x = b\).
- In our example, the integral \( \pi \int_{0}^{2} (x^2)^2 \, dx \) calculates the volume sweeping out around the \(x\)-axis, transforming our 2D shape into a 3D solid.
- The result we obtain, through careful integration and accounting for the limits, directly gives a concrete volume of the space revolutionized by the function about the axis.
Antiderivative
An antiderivative, also known as an indefinite integral, is essentially the reverse process of differentiation. It's a function whose derivative is the original function you're considering. Understanding antiderivatives is crucial for solving integration problems:
- In our problem, finding the volume required us to first determine the antiderivative of \( x^4 \), which represents the solid's cross-sectional area when expressed as \( [f(x)]^2 \).
- The process involved finding a function whose derivative returns \( x^4 \). For polynomials, a function like \( \int x^4 \, dx = \frac{x^5}{5} + C \) does this, where \(C\) is a constant of integration that is determined by evaluating the definite endpoints.