Math Problem Statement

Find the volume of the solid obtained by rotating the region in the first quadrant bounded by the curves x=0, y=1, x=y^3, about the line y=1.

Solution

To solve this problem, we will use the method of cylindrical shells. We are rotating the region in the first quadrant bounded by the curves x=0x = 0, y=1y = 1, x=y3x = y^3, about the line y=1y = 1.

Step-by-step solution:

  1. Understanding the region:

    • The curve x=y3x = y^3 and the line y=1y = 1 bound the region, with x=0x = 0 as the left boundary. We are rotating around the horizontal line y=1y = 1.
  2. Set up the volume integral using cylindrical shells:

    • For a solid generated by rotating about a horizontal line, the height of each shell is based on the xx-coordinate of the boundary, and the radius of the shell is the vertical distance from the line of rotation.

    • The radius of the shell is r(y)=1yr(y) = 1 - y (since the rotation is about y=1y = 1).

    • The height of the shell is determined by the boundary curve x=y3x = y^3.

    • The volume of a cylindrical shell is given by: dV=2π(radius)(height)(thickness)dV = 2\pi \cdot (\text{radius}) \cdot (\text{height}) \cdot (\text{thickness}) So, the volume element is: dV=2π(1y)y3dydV = 2\pi \cdot (1 - y) \cdot y^3 \, dy

  3. Determine limits of integration:

    • The region is bounded by y=0y = 0 and y=1y = 1.
  4. Set up and compute the integral: The total volume VV is: V=012π(1y)y3dyV = \int_0^1 2\pi (1 - y) y^3 \, dy We can now solve this integral step by step.

Let's proceed to compute the integral.The volume of the solid obtained by rotating the region around the line y=1y = 1 is π10\frac{\pi}{10}.

Would you like further details or have any other questions?

Here are five related questions for deeper understanding:

  1. How would the solution change if the region were rotated around the xx-axis?
  2. What happens if we rotate the region around a different horizontal line, such as y=2y = 2?
  3. Can this problem be solved using the disk/washer method instead of cylindrical shells?
  4. What is the volume if the curve x=y3x = y^3 is replaced with another function, such as x=y2x = y^2?
  5. How would the limits of integration change if the region extended into negative yy-values?

Tip: The method of cylindrical shells is often useful when the axis of rotation is parallel to the boundaries of the region you're integrating.

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Math Problem Analysis

Mathematical Concepts

Calculus
Volume of Solids of Revolution
Cylindrical Shells Method

Formulas

Volume element of cylindrical shell: dV = 2π(radius)(height)(thickness)
Integral for volume: V = ∫2π(radius)(height) dy

Theorems

Cylindrical Shells Method

Suitable Grade Level

Grades 11-12 (High School Calculus)