Question Details

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

Options

A

π/4

B

π/2

C

π

D

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:

x=y2

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:

y2=x

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 V of a solid of revolution rotated around the x-axis is given by:

V=abπ[f(x)]2dx

Here, the radius squared is [f(x)]2=y2=x, and the limits of integration are from x=0 to x=1.

Substituting these values into the volume formula:

V=01πxdx

We can pull the constant π outside the integral:

V=π01xdx

Integrating x with respect to x gives:

V=π[x22]01

Evaluating this at the limits 1 and 0:

V=π(122-022)

V=π(12)=π2

Thus, the volume of the solid of rotation is indeed π/2.

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