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mediumMCQPYQs Based Test - 09 : Line, Surface, and Volume IntegralsGeneral
1 mark (−0.33)

Determine the volume of the solid of revolution formed when the curve y = 2 is rotated 360° about the x-axis between the limits x = 0 to x = 3.

  1. A
    24π
  2. B
  3. C
    12π
  4. D

Solution & Step-by-step Explanation

To determine the volume of the solid of revolution formed by rotating a curve about an axis, we commonly use methods like the Disk Method or the Washer Method. In this specific problem, we are given a simple curve, y = 2, which is a horizontal line. This line is rotated 360° about the x-axis between the limits x = 0 and x = 3.

Volume Calculation using the Disk Method

When a region is rotated about the x-axis, and the solid generated has no hole, the Disk Method is the most suitable approach. The formula for the volume V using the Disk Method for a function y = f(x) rotated about the x-axis from x = a to x = b is given by:



Let's break down the components given in the problem:

- The function is .
- The axis of revolution is the x-axis.
- The lower limit of integration is .
- The upper limit of integration is .

Applying the Disk Method to the Curve y=2

Now, we will substitute these values into the Disk Method formula to calculate the volume of the solid of revolution.

Step 1: Set up the integral.

Substitute , , and into the volume formula:



Step 2: Simplify the integrand.

Square the function value:



Rearrange the constant:



Step 3: Evaluate the integral.

The integral of is . So, we evaluate from to :



Step 4: Apply the limits of integration.

Substitute the upper limit and subtract the substitution of the lower limit:



Step 5: Calculate the final volume.





The volume of the solid of revolution formed is cubic units. This solid is essentially a cylinder with radius 2 and height 3. The volume of a cylinder is given by . Here, and , so , which confirms our integration result.

Practice this question

Try it yourself before checking the explanation above.

Determine the volume of the solid of revolution formed when the curve y = 2 is rotated 360° about the x-axis between the limits x = 0 to x = 3.
A
24π
B
C
12π
D

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