Finding the volume of a solid when the solid is a region rotated around a line

In summary, the problem asks to find the volume of a solid obtained by rotating the region bounded by the curves y = x^(6) and y = 1 around the axis y = 2. The region is fin-shaped and is rotated to form a cylinder with missing inside and flat sides. The thickness of the cylinder is delta y and the radius is 2-y, with a circumference of 2pi(2-y). The height of the cylinder is y^(1/6). The integral set up to solve the problem is 0 to 1 of 2pi(2-y)y^(1/6)dy, which gives the wrong answer of 2pi(12/7-6/13). However, the
  • #1
jlt90
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Homework Statement



Find the volume of the solid obtained by rotating the region bounded by the given curves about the specified axis.

y = x^(6), y = 1 about y = 2

Homework Equations





The Attempt at a Solution


So i drew a picture and found the region to be fin shaped from 0 to 1 on both the x and y axis. I then rotated it around y=2 to get a cylinder with a missing inside with flat sides and an outside that is curved. I believe the thickness of these cylinders is delta y, so I'm putting everything in terms of y. I then find the radius to be 2-y, since the center of the cylinder is at y=2 and at y=0 the radius is 2, at y=1 it is 1. So that gives me a circumference of 2pi(2-y). Next I find the height, which my picture shows as the x values when x=y^(1/6), so my h=y^(1/6). I am now able to set up my integral so that 0int1 2pi(2-y)y^(1/6)dy. When I evaluate this, I come up 2pi(12/7-6/13) which is the wrong answer. Can someone please tell me where I went wrong?
 
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  • #2
I found where I made my mistake :) So no need to help me anymore. Thanks anyways.
 

1. What is the formula for finding the volume of a solid when it is rotated around a line?

The formula for finding the volume of a solid when it is rotated around a line is π∫ab(f(x))2dx, where f(x) represents the function that defines the solid and a and b represent the limits of integration.

2. How do I determine the limits of integration for finding the volume of a solid?

The limits of integration can be determined by finding the points of intersection between the function that defines the solid and the axis of rotation. These points will serve as the limits of integration.

3. Can I use this formula for any solid that is rotated around a line?

Yes, this formula can be used for any solid that is rotated around a line, as long as the solid can be represented by a function and the limits of integration can be determined.

4. Is there a different formula for finding the volume of a solid when it is rotated around a line in three dimensions?

Yes, there is a different formula for finding the volume of a solid when it is rotated around a line in three dimensions. This formula involves using triple integrals and is more complex than the two-dimensional formula.

5. Can I use this formula to find the volume of irregularly shaped solids?

No, this formula is only applicable for finding the volume of solids that can be represented by a function and rotated around a line. For irregularly shaped solids, other methods such as using a displacement method or approximating with smaller regular shapes may be necessary to find the volume.

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