Math Problem Statement

Use cylindrical shells to find the volume of the solid obtained by rotating the region bounded on the right by the graph of g(y)=8/y and on the left by the y-axis for 4≤y≤6, about the x-axis. Round your answer to the nearest hundredth position.

Solution

We can use the method of cylindrical shells to find the volume of the solid obtained by rotating the region bounded by the graph of g(y)=8yg(y) = \frac{8}{y} (on the right), the yy-axis (on the left), and between y=4y = 4 and y=6y = 6, about the xx-axis.

Step-by-Step Approach:

  1. Formula for volume using cylindrical shells: The formula for the volume using cylindrical shells is:

    V=2πabradius×heightdyV = 2\pi \int_{a}^{b} \text{radius} \times \text{height} \, dy

    • The radius is the distance from the axis of rotation (the xx-axis) to a point on the curve, which is yy.
    • The height of each cylindrical shell is given by the function g(y)=8yg(y) = \frac{8}{y}.

    So, the formula becomes:

    V=2π46y8ydyV = 2\pi \int_{4}^{6} y \cdot \frac{8}{y} \, dy

  2. Simplifying the integral: Notice that y8y=8y \cdot \frac{8}{y} = 8, so the integral simplifies to:

    V=2π468dyV = 2\pi \int_{4}^{6} 8 \, dy

  3. Evaluate the integral: Now, we integrate:

    468dy=8(y)46=8(64)=8×2=16\int_{4}^{6} 8 \, dy = 8(y) \Big|_4^6 = 8(6 - 4) = 8 \times 2 = 16

  4. Final volume: Multiply by 2π2\pi:

    V=2π×16=32πV = 2\pi \times 16 = 32\pi

  5. Approximating the result: Now, approximate VV:

    V32×3.1416=100.53V \approx 32 \times 3.1416 = 100.53

Final Answer:

The volume of the solid is approximately 100.53\boxed{100.53} cubic units.

Would you like further details or clarification? Here are some related questions:

  1. How does the method of cylindrical shells differ from the disk method?
  2. What happens if the region is rotated about the y-axis instead?
  3. How do we handle problems where the bounds are more complex?
  4. Can we use cylindrical shells if the function was instead g(y)=y8g(y) = \frac{y}{8}?
  5. How would the solution change if the limits were from 3 to 5?

Tip: When solving problems using cylindrical shells, always check if the integral simplifies before performing complex operations—it can save time!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Cylindrical Shells Method
Integral Calculus
Volume of Solids of Revolution

Formulas

V = 2π ∫[a,b] (radius × height) dy
g(y) = 8/y

Theorems

Method of Cylindrical Shells
Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12 or College Level