Math Problem Statement

Set up triple integrals for the volume of the sphere

rhoρequals=55

in

Bold a.a.

​spherical,

Bold b.b.

​cylindrical, and

Bold c. rectangularc. rectangular

Solution

We are asked to set up triple integrals for the volume of a sphere with radius ρ=5\rho = 5 in three different coordinate systems: spherical, cylindrical, and rectangular coordinates.

a. Spherical Coordinates:

In spherical coordinates, the volume element is given by dV=ρ2sinϕdρdθdϕdV = \rho^2 \sin \phi \, d\rho \, d\theta \, d\phi, where:

  • ρ\rho is the radial distance (from the origin),
  • θ\theta is the azimuthal angle (in the xy-plane, 0 to 2π2\pi),
  • ϕ\phi is the polar angle (from the positive z-axis, 0 to π\pi).

The limits for a sphere of radius 5 are:

  • ρ\rho goes from 0 to 5,
  • θ\theta goes from 0 to 2π2\pi,
  • ϕ\phi goes from 0 to π\pi.

The integral for the volume is:

V=02π0π05ρ2sinϕdρdϕdθV = \int_0^{2\pi} \int_0^{\pi} \int_0^5 \rho^2 \sin \phi \, d\rho \, d\phi \, d\theta

b. Cylindrical Coordinates:

In cylindrical coordinates, the volume element is given by dV=rdzdrdθdV = r \, dz \, dr \, d\theta, where:

  • rr is the radial distance in the xy-plane,
  • θ\theta is the azimuthal angle (0 to 2π2\pi),
  • zz is the height (from 25r2-\sqrt{25 - r^2} to 25r2\sqrt{25 - r^2}, derived from the equation of the sphere x2+y2+z2=25x^2 + y^2 + z^2 = 25).

The limits are:

  • rr goes from 0 to 5,
  • θ\theta goes from 0 to 2π2\pi,
  • zz goes from 25r2-\sqrt{25 - r^2} to 25r2\sqrt{25 - r^2}.

The integral for the volume is:

V=02π0525r225r2rdzdrdθV = \int_0^{2\pi} \int_0^5 \int_{-\sqrt{25 - r^2}}^{\sqrt{25 - r^2}} r \, dz \, dr \, d\theta

c. Rectangular Coordinates:

In rectangular coordinates, the volume element is dV=dxdydzdV = dx \, dy \, dz. The equation of the sphere is x2+y2+z2=25x^2 + y^2 + z^2 = 25, so the limits on xx, yy, and zz are determined by this equation.

The limits are:

  • xx goes from 5-5 to 55,
  • yy goes from 25x2-\sqrt{25 - x^2} to 25x2\sqrt{25 - x^2},
  • zz goes from 25x2y2-\sqrt{25 - x^2 - y^2} to 25x2y2\sqrt{25 - x^2 - y^2}.

The integral for the volume is:

V=5525x225x225x2y225x2y2dzdydxV = \int_{-5}^{5} \int_{-\sqrt{25 - x^2}}^{\sqrt{25 - x^2}} \int_{-\sqrt{25 - x^2 - y^2}}^{\sqrt{25 - x^2 - y^2}} dz \, dy \, dx


Would you like more details or have any questions?

Here are 5 related questions:

  1. How do you evaluate the spherical integral for a general radius ρ\rho?
  2. How does the Jacobian affect the volume integral in different coordinates?
  3. Can you derive the limits for the cylindrical case from the equation of the sphere?
  4. What are the advantages of using spherical coordinates for spherical symmetry?
  5. How would the integrals change if the sphere were shifted from the origin?

Tip: When dealing with spherical symmetry, spherical coordinates simplify the problem and reduce the complexity of the integrals.

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Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Triple Integrals
Coordinate Systems
Spherical Coordinates
Cylindrical Coordinates
Rectangular Coordinates

Formulas

Volume element in spherical coordinates: dV = ρ^2 sin(φ) dρ dθ dφ
Volume element in cylindrical coordinates: dV = r dz dr dθ
Volume element in rectangular coordinates: dV = dx dy dz
Equation of the sphere: x^2 + y^2 + z^2 = 25

Theorems

Jacobian determinant for coordinate transformations

Suitable Grade Level

Undergraduate - Calculus III