Find the volume using shell and disk method

Click For Summary

Discussion Overview

The discussion revolves around calculating the volume of a solid using both the shell and disk methods in calculus. Participants are exploring the integration techniques involved and addressing specific calculations related to the volume formula.

Discussion Character

  • Mathematical reasoning, Homework-related

Main Points Raised

  • One participant expresses difficulty in obtaining the correct answer for the volume calculation.
  • Another participant presents a volume expression involving integrals, specifically $\displaystyle V = 18\pi - 2\pi \int_0^{\pi/2} x \cos{x} \, dx$ and $\displaystyle V = 18\pi - \pi \int_0^1 [\arccos{y}]^2 \, dy$.
  • A subsequent post repeats the volume expression and questions the origin of the term $18\pi$.
  • Another participant provides a formula for the volume of a hemisphere, $\dfrac{2\pi r^3}{3}$, specifying $r = 3$, which may relate to the $18\pi$ term.

Areas of Agreement / Disagreement

Participants are seeking clarification on the calculations, particularly the origin of the $18\pi$ term, indicating that there is no consensus on this aspect yet.

Contextual Notes

The discussion includes unresolved mathematical steps regarding the integration and the specific calculations leading to the volume expression.

jaychay
Messages
58
Reaction score
0
Can you please help me ?
I have tried to do it but I end up getting the wrong answer.

Untitled.png
 
Physics news on Phys.org
$\displaystyle V = 18\pi - 2\pi \int_0^{\pi/2} x \cos{x} \, dx$

$\displaystyle V = 18\pi - \pi \int_0^1 [\arccos{y}]^2 \, dy$
 
Last edited by a moderator:
skeeter said:
$\displaystyle V = 18\pi - 2\pi \int_0^{\pi/2} x \cos{x} \, dx$

$\displaystyle V = 18\pi - \pi \int_0^1 [\arccos{y}]^2 \, dy$
Can you tell me where did 18 pi come from ?
 
jaychay said:
Can you tell me where did 18 pi come from ?

volume of a hemisphere is $\dfrac{2\pi r^3}{3}$ and $r = 3$
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 6 ·
Replies
6
Views
7K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
2
Views
3K
  • · Replies 13 ·
Replies
13
Views
3K