Physics I / Triple Integrals
Practice question · Multiple choice

To integrate over a ball of radius RR centred at the origin, which coordinate system makes the limits simplest, and why?

Hints
  1. The dream scenario is constant limits, a coordinate box. Which system’s coordinates does the sphere’s equation (x2+y2+z2=R2x^2+y^2+z^2=R^2) collapse into?
  2. In spherical coordinates that equation reads simply ρ=R\rho = R.
Show the answer

B. Spherical: the ball becomes a box in ρ,φ,θ\rho,\varphi,\theta

Why

Match the coordinates to the region’s symmetry and curved boundaries flatten into constant limits: the ball is literally a rectangular box in (ρ,φ,θ)(\rho, \varphi, \theta). The price, the volume factor ρ2sinφ\rho^{2}\sin\varphi, is far cheaper than nested square roots.

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