A parabola x = y2 with 0 ≤ x ≤ 1 is shown in the figure. The volume of the solid of rotation obtained by rotating the shaded area by 360° around the x–axis is
Correct Answer :
π/2
Solution :
The correct option is π/2.
To find the volume of the solid of rotation obtained by rotating the shaded area 360° around the x-axis, we use the method of disks/washers.
The given equation of the parabola is:
Since the rotation is about the x-axis, we express the radius of the cross-sectional disks in terms of x. Rearranging the equation for y, we get:
The shaded region is bounded by the curve, the x-axis, and the vertical line from x = 0 to x = 1. The formula for the volume of a solid of revolution rotated around the x-axis is given by:
Here, the radius squared is , and the limits of integration are from to .
Substituting these values into the volume formula:
We can pull the constant π outside the integral:
Integrating with respect to gives:
Evaluating this at the limits 1 and 0:
Thus, the volume of the solid of rotation is indeed π/2.
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