Question

Why can this solid of revolution problem not be solved with shell? (typing question w/ eqation maker)

Answer 1

\[For the formula:2\pi \int\limits\limits_{a}^{b}phdx\]
Where a = 0, b=4 p=x and h=\[\sqrt{x}\]

Answer 2

After plugging in and evaulating I am getting \[128\pi/5\], my texbook answer is \[32\pi/5\] Am i making an error or is shell method just impossible in this scenario? If it is not possible, please explain why, thanks!

Answer 3

Please write the question as it was asked. That way we take a fresh take, a fresh look at it.

Answer 4

Using the shell method, find the volume of: \[\sqrt(x)\] with bounds [0,4] after it has been revolved around the y axis.

Answer 5

and the bounds on the y is 0,2, but that is not relevant to the formula

Answer 6

(y-axis that is)

Answer 7

It is confusing '...and the bounds of y is 0,2' what is that info.

Answer 8

It just means there is a line at y=2

Answer 9

Is that in the question, or is that something you figured out?

Answer 10

if there wasn't it wouldnt make a shape when revolved cause the top would be endless

Answer 11

There is actually a picture, hold on one second

Answer 12

If you can imagine these graphs zoomed out more: http://www.wolframalpha.com/input/?i=y%3Dsqrt%28x%29%2C+y%3D2

Answer 13

But what is the actual question? You wrote the question and then you added something. It is that part of the question.

Answer 14

The actual question is exactly what I wrote only it asked to solve with disk method

Answer 15

Using the shell method, find the volume of:
(√x)
with bounds [0,4] after it has been revolved around the y axis.

Answer 16

only using disk method

Answer 17

Disk or shell?

Answer 18

It askd for disk, I am trying shell

Answer 19

But I got an incorrect answer so I am tring to figure out if shell does not work or if i messed up

Answer 20

Ok, here is an illustration: http://www.scriblink.com/index.jsp?act=phome&roomid=1650&KEY=9445365509101FCAF650C4612FFA0010

Answer 21

Any way, your answer is not far off. Just write your work on your whiteboard and we will see if you made a little arithmetic or algebra error.

Answer 22

ok

Answer 23

Done

Answer 24

You checking?

Answer 25

Yes

Answer 26

I know that shell method is not the correct method in some cases but I do not know why

Answer 27

So I am trying to see if this is one of those cases so I can figure out why

Answer 28

I get 128pi/5, but if I understand you it asked for disk method, did you get it right in disk method?

Answer 29

yea, I got it right with disk

Answer 30

32pi/5

Answer 31

Do we have a pickle?

Answer 32

I'm checking.

Answer 33

I think you have to convert it in terms of y. And then use some y. In your diagram you used some x. It is good that you investigate different techniques you would be very successful. When you have time change f(x) to g(y) and so on.

Answer 34

Ah yea, I think that may be it

Answer 35

I'll give that a try, thanks

Answer 36

It wont let me give you a medal?