Math Problem Statement

Use the shell method to write and evaluate the definite integral that represents the volume of the solid generated by revolving the plane region about the x-axis. y = x from 0 to 2

Solution

To find the volume of the solid generated by revolving the region bounded by the curve y=xy = x from x=0x = 0 to x=2x = 2 around the x-axis using the shell method, follow these steps:

1. Set up the shell method formula

The formula for the volume using the shell method when revolving around the x-axis is:

V=2πab(radius)(height)dxV = 2\pi \int_{a}^{b} (radius)(height) \, dx

Here:

  • The radius is the distance from the x-axis to the strip, which is simply yy.
  • The height of each cylindrical shell is the function of yy, which is x=yx = y.

2. Define the limits of integration

Since we're integrating with respect to yy, we need to change the limits to match the yy-coordinates:

  • At x=0x = 0, y=0y = 0.
  • At x=2x = 2, y=2y = 2.

Thus, the limits of integration are from y=0y = 0 to y=2y = 2.

3. Write the integral for the volume

The height is given by x=yx = y, and the radius is yy. Thus, the integral becomes:

V=2π02y(y)dyV = 2\pi \int_{0}^{2} y(y) \, dy V=2π02y2dyV = 2\pi \int_{0}^{2} y^2 \, dy

4. Evaluate the integral

Now, we evaluate the definite integral:

y2dy=y33\int y^2 \, dy = \frac{y^3}{3}

Apply the limits of integration:

V=2π[y33]02V = 2\pi \left[ \frac{y^3}{3} \right]_{0}^{2}

V=2π(233033)V = 2\pi \left( \frac{2^3}{3} - \frac{0^3}{3} \right)

V=2π(830)V = 2\pi \left( \frac{8}{3} - 0 \right)

V=2π83V = 2\pi \cdot \frac{8}{3}

V=16π3V = \frac{16\pi}{3}

Final Answer:

The volume of the solid generated by revolving the region bounded by y=xy = x from x=0x = 0 to x=2x = 2 about the x-axis is:

V=16π3V = \frac{16\pi}{3}


Do you want more details or have any further questions on this problem?

Here are 5 related questions you might consider:

  1. How would the shell method differ if revolving around the y-axis?
  2. What is the difference between the shell method and the disk method?
  3. Can the same integral be solved using the disk/washer method for this problem?
  4. How do you interpret the result geometrically in terms of volume?
  5. What would change if the region was y=x2y = x^2 instead of y=xy = x?

Tip: Always check the axis of rotation carefully, as it determines the setup for the shell method or disk method.

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Math Problem Analysis

Mathematical Concepts

Calculus
Volume of Solids of Revolution
Shell Method
Definite Integral

Formulas

V = 2π ∫ (radius)(height) dx
∫ y^2 dy = (y^3)/3

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

College-level Calculus