Volume of Hollow Solids of Revolution
This page introduces the washer method for calculating the volume of hollow solids of revolution, an advanced application of integration for volume formulas in calculus.
The washer method is used when a region bounded by two functions, f(x) and g(x), is rotated around an axis, creating a hollow solid. The general formula for the volume is:
V = π ∫ [R² - r²] dx
Where R is the outer radius (distance from the axis to the outer function) and r is the inner radius (distance from the axis to the inner function).
Definition: The washer method involves subtracting the volume of the inner solid from the volume of the outer solid to find the volume of the hollow region.
For rotation around the x-axis, this formula becomes:
V = π ∫ [f(x)² - g(x)²] dx
Highlight: The washer method is a powerful tool in AP Calculus AB volume of revolution problems, allowing for the calculation of complex hollow shapes.
The page provides a visual representation of a cross-section of a hollow solid, illustrating how the area of each "washer" is calculated by subtracting the area of the inner circle from the area of the outer circle.
Example: For a region bounded by f(x) = x² and g(x) = x, rotated around the x-axis from x = 0 to x = 1, the volume would be calculated as V = π ∫₀¹ (x⁴ - x²) dx.
This method is crucial for solving advanced problems in calculus, particularly in AP calculus AB volume of revolution frq (free-response questions) and other challenging applications.