Volume of a solid using shells

In summary, the conversation is about finding the volume of a region bounded by a curve and rotated around a given line. The speaker's teacher has a solution of 4∏/15, while the speaker got 11∏/210. The speaker is unsure of where they went wrong and notes that having a sketch of the solid can be helpful in solving the problem.
  • #1
Feodalherren
605
6

Homework Statement



Find the volume of the region bounded by the curve y=x^(1/3) and y=x rotated about the line y=1.

Homework Equations





The Attempt at a Solution


My teacher's solution is 4∏/15 . I got 11∏/210.

http://imageshack.us/a/img443/426/0zhs.jpg
http://imageshack.us/a/img443/426/0zhs.jpg
Where am I going wrong?
 
Last edited by a moderator:
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  • #2
Feodalherren said:

Homework Statement



Find the volume of the region bounded by the curve y=x^(1/3) and y=x rotated about the line y=1.

Homework Equations





The Attempt at a Solution


My teacher's solution is 4∏/15 . I got 11∏/210.

http://imageshack.us/a/img443/426/0zhs.jpg
http://imageshack.us/a/img443/426/0zhs.jpg
Where am I going wrong?

You don't have a sketch of the solid of revolution, so I can't tell what you did. However, it looks like you didn't rotate the region around the line y = 1. I find that it's helpful to have a sketch of the solid, at least a cross-section of it, showing the typical volume element.
 
Last edited by a moderator:

1. What is the formula for finding the volume of a solid using shells?

The formula for finding the volume of a solid using shells is V = ∫ab 2πrh(x)dx, where r is the radius of the shell and h(x) is the height of the solid at a given point x.

2. How do you determine the limits of integration when using the shell method?

The limits of integration for the shell method are determined by finding the points of intersection between the curves that define the solid and the axis of rotation. These points will be used as the upper and lower limits of integration.

3. Can the shell method be used to find the volume of any solid?

No, the shell method can only be used to find the volume of solids that can be rotated around an axis. This method is commonly used for finding the volume of objects such as cylinders, cones, and spheres.

4. What is the difference between the disk method and the shell method?

The disk method and the shell method are both used to find the volume of solids, but they differ in the shape of the cross-sections used for integration. The disk method uses circles as the cross-sections, while the shell method uses cylindrical shells.

5. Are there any limitations to using the shell method?

One limitation of the shell method is that it can only be used for solids with a simple axis of rotation. If the axis of rotation is more complex, it may be necessary to use other methods, such as the disk method or the washer method, to find the volume of the solid.

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