How Do You Correctly Set Up a Triple Integral Over a Sphere?

  • Thread starter Thread starter PsychonautQQ
  • Start date Start date
  • Tags Tags
    Integrating Sphere
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
4 replies · 2K views
PsychonautQQ
Messages
781
Reaction score
10

Homework Statement


Triple Integral: x^2+y^2+z^2dV over the ball x^2+y^2+z^2 ≤ 9


Homework Equations





The Attempt at a Solution


so With my integral I had
Triple Integral: p^3sin∅dpd∅dθ
0≥p≥3
0≥∅≥∏
0≥θ≤2∏

Does this look like the correct integral? I swear it is! Yet my answer is wrong. I rebuke these foul math gods!
 
Physics news on Phys.org
PsychonautQQ said:

Homework Statement


Triple Integral: x^2+y^2+z^2dV over the ball x^2+y^2+z^2 ≤ 9


Homework Equations





The Attempt at a Solution


so With my integral I had
Triple Integral: p^3sin∅dpd∅dθ
0≥p≥3
0≥∅≥∏
0≥θ≤2∏

Does this look like the correct integral? I swear it is! Yet my answer is wrong. I rebuke these foul math gods!


[tex] \iiint_{r \leq 3} r^2\,dV = \int_0^{2\pi} \int_0^{\pi} \int_0^3 (r^2) (r^2 \sin \theta) \,dr\,d\theta\,d\phi[/tex]
 
pasmith said:
[tex] \iiint_{r \leq 3} r^2\,dV = \int_0^{2\pi} \int_0^{\pi} \int_0^3 (r^2) (r^2 \sin \theta) \,dr\,d\theta\,d\phi[/tex]
That looks to me the same as PsychonautQQ posted, just with some of the ≤/≥ turned around the right way and with theta and phi swapped.
PsychonautQQ, what answer do you get and what is it supposed to be? Pls post your working in solving the integral.
 
haruspex said:
That looks to me the same as PsychonautQQ posted, just with some of the ≤/≥ turned around the right way and with theta and phi swapped.

And the correct expression for the volume element ...