Math Problem Statement

Find the volume of the solid generated by revolving the region bounded by the curve y = √(16 - x^2) and y = 0 about the x-axis.

Solution

To find the volume of the solid generated by revolving the region bounded by the curve y=16x2y = \sqrt{16 - x^2} and the line y=0y = 0 about the x-axis, we can use the disk method.

  1. Identify the Region to Revolve: The curve y=16x2y = \sqrt{16 - x^2} represents the upper half of a circle with radius 4, centered at the origin. This curve intersects the x-axis (where y=0y = 0) at x=4x = -4 and x=4x = 4.

  2. Set Up the Integral for the Volume: The volume VV of the solid formed by revolving this region about the x-axis is given by: V=π44(16x2)2dxV = \pi \int_{-4}^{4} \left( \sqrt{16 - x^2} \right)^2 \, dx

  3. Simplify the Integral: Since (16x2)2=16x2\left( \sqrt{16 - x^2} \right)^2 = 16 - x^2, the volume integral becomes: V=π44(16x2)dxV = \pi \int_{-4}^{4} (16 - x^2) \, dx

  4. Evaluate the Integral: Split the integral: V=π(4416dx44x2dx)V = \pi \left( \int_{-4}^{4} 16 \, dx - \int_{-4}^{4} x^2 \, dx \right)

  5. Calculate Each Part:

    • For 4416dx\int_{-4}^{4} 16 \, dx: 4416dx=16(4(4))=168=128\int_{-4}^{4} 16 \, dx = 16 \cdot (4 - (-4)) = 16 \cdot 8 = 128
    • For 44x2dx\int_{-4}^{4} x^2 \, dx: Because x2x^2 is an even function, we can compute this integral from 00 to 44 and double it: 44x2dx=204x2dx=2[x33]04=2643=1283\int_{-4}^{4} x^2 \, dx = 2 \int_{0}^{4} x^2 \, dx = 2 \cdot \left[ \frac{x^3}{3} \right]_{0}^{4} = 2 \cdot \frac{64}{3} = \frac{128}{3}
  6. Combine Results: Substitute back into the volume formula: V=π(1281283)=π3841283=π2563=256π3V = \pi \left( 128 - \frac{128}{3} \right) = \pi \cdot \frac{384 - 128}{3} = \pi \cdot \frac{256}{3} = \frac{256\pi}{3}

Final Answer:

The volume of the solid is: V=256π3V = \frac{256\pi}{3}

Would you like further clarification on any part of this process?


Related Questions:

  1. How would the solution change if the region were revolved around the y-axis instead?
  2. What is the volume if we revolve only the first quadrant portion of the region?
  3. How do we apply the washer method for a similar volume problem?
  4. Can this integral be solved using polar coordinates, and what would that look like?
  5. What would the setup be if we revolved this region about a line y=cy = c where c>0c > 0?

Tip: For regions that are symmetric about an axis, consider integrating only half the region and then doubling the result to simplify calculations.

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Math Problem Analysis

Mathematical Concepts

Calculus
Volume of Solids of Revolution
Disk Method
Integration

Formulas

Volume of revolution about x-axis: V = π ∫ [f(x)]^2 dx
Simplification of integral with √(16 - x^2) representing half-circle radius function

Theorems

Disk Method

Suitable Grade Level

Grade 12 or College Calculus