Calculus For The Life Sciences
2nd Edition
ISBN:9780321964038
Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Publisher:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Chapter8: Further Techniques And Applications Of Integration
Section8.3: Volume And Average Value
Problem 22E
Related questions
Question
![### Finding Volumes Using the Method of Cylindrical Shells
This section will explain how to find the volume generated by rotating a region around a given axis using the method of cylindrical shells. Please ensure to enter exact answers in terms of π (pi).
#### Example Problems
1. **Problem (a)**
Given the function:
\[ y = 3x - x^2, \, x = 0 \]
Find the volume of the solid formed by rotating the region around the y-axis.
\[ \text{Volume} = \underline{\hspace{80pt}} \]
2. **Problem (b)**
Given the function:
\[ y = \frac{1}{x^2}, \, 1 \leq x \leq 3, \, y = 0 \]
Find the volume of the solid formed by rotating the region around the y-axis.
\[ \text{Volume} = \underline{\hspace{80pt}} \]
### Explanation of the Method of Cylindrical Shells
The method of cylindrical shells involves the following steps:
1. **Identify the region to be rotated**: Define the boundaries of the region in terms of the given function(s).
2. **Shell element**: Consider an infinitesimally thin vertical strip of width \( \Delta x \) within the region.
3. **Radius of the shell**: Determine the distance of this strip from the axis of rotation.
4. **Height of the shell**: Given by the function value at a specific \( x \)-coordinate.
5. **Volume of the shell**: The volume of the cylindrical shell is given by \( 2\pi(\text{radius})(\text{height})(\Delta x) \).
6. **Integration**: Integrate this expression over the interval to find the total volume.
This method is particularly useful when the strip is easier to describe vertically rather than horizontally.
#### General Formula
\[ V = \int_{a}^{b} 2\pi x f(x) \, dx \]
Where:
- \( f(x) \) is the function describing the height of the shell.
- \( x \) is the distance from the y-axis to the shell.
Remember to check the limits of integration according to the given bounds of \( x \).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fb4c907f3-6692-4a58-8d85-7b416968270c%2Fb8e62c45-5b17-4daf-af96-84f77488da7d%2F4gd5ny_processed.jpeg&w=3840&q=75)
Transcribed Image Text:### Finding Volumes Using the Method of Cylindrical Shells
This section will explain how to find the volume generated by rotating a region around a given axis using the method of cylindrical shells. Please ensure to enter exact answers in terms of π (pi).
#### Example Problems
1. **Problem (a)**
Given the function:
\[ y = 3x - x^2, \, x = 0 \]
Find the volume of the solid formed by rotating the region around the y-axis.
\[ \text{Volume} = \underline{\hspace{80pt}} \]
2. **Problem (b)**
Given the function:
\[ y = \frac{1}{x^2}, \, 1 \leq x \leq 3, \, y = 0 \]
Find the volume of the solid formed by rotating the region around the y-axis.
\[ \text{Volume} = \underline{\hspace{80pt}} \]
### Explanation of the Method of Cylindrical Shells
The method of cylindrical shells involves the following steps:
1. **Identify the region to be rotated**: Define the boundaries of the region in terms of the given function(s).
2. **Shell element**: Consider an infinitesimally thin vertical strip of width \( \Delta x \) within the region.
3. **Radius of the shell**: Determine the distance of this strip from the axis of rotation.
4. **Height of the shell**: Given by the function value at a specific \( x \)-coordinate.
5. **Volume of the shell**: The volume of the cylindrical shell is given by \( 2\pi(\text{radius})(\text{height})(\Delta x) \).
6. **Integration**: Integrate this expression over the interval to find the total volume.
This method is particularly useful when the strip is easier to describe vertically rather than horizontally.
#### General Formula
\[ V = \int_{a}^{b} 2\pi x f(x) \, dx \]
Where:
- \( f(x) \) is the function describing the height of the shell.
- \( x \) is the distance from the y-axis to the shell.
Remember to check the limits of integration according to the given bounds of \( x \).
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