Comparing Volumes of Revolution
Consider four solids obtained by revolving the regions described in the table about the x-axis over the interval $$[0,1]$$. Assume that the volume for Region 1 is computed as the area between the curves $$y=x$$ (top) and $$y=x^2$$ (bottom), while Regions 2, 3, and 4 are generated by revolving the area under the curves $$y=x^2$$, $$y=x$$, and $$y=\sqrt{x}$$ respectively. Without performing the full integration, determine the relative sizes of these volumes and rank the four regions in increasing order of volume.
| Region of Revolution | Bounded by Curves | Axis of Rotation | Interval | Volume Formula |
|---|---|---|---|---|
| Region 1 | Between $$y=x^2$$ and $$y=x$$ | x-axis | Intersection | $$V=\pi\int (x-x^2)\,dx$$ |
| (Washers) | [0,1] | (Exact volume: not required) | ||
| Region 2 | Area under $$y=x^2$$ | x-axis | [0,1] | $$\pi\int (x^2)^2\,dx$$ |
| Region 3 | Area under $$y=x$$ | x-axis | [0,1] | $$\pi\int x^2\,dx$$ |
| Region 4 | Area under $$y=\sqrt{x}$$ | x-axis | [0,1] | $$\pi\int (\sqrt{x})^2\,dx$$ |
A
Region 1, Region 2, Region 4, Region 3
B
Region 1, Region 2, Region 3, Region 4
C
Region 2, Region 1, Region 4, Region 3
D
Region 1, Region 4, Region 2, Region 3
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