Volume of a Sphere: Solve with Calculus & Integration

Summing the volumes of all the disks from x = -r to x = r will give an approximation of the volume of revolution. As the thickness of the disks becomes infinitesimally small, the approximation becomes exact and the integral gives the exact value of the volume. In summary, the volume of a sphere of radius r can be found by integrating the cross-sectional area of a disk, which is πy^2, from -r to r, and multiplying by the thickness of the disk, dx. This gives the formula V = ∫(πy^2)dx from -r to r, which simplifies to (4/3)πr^3.
  • #1
Feodalherren
605
6

Homework Statement



Show that the volume of a sphere of radius r is

V = (4/3)πr^2

Homework Equations



calculus, integration

The Attempt at a Solution



I have the solution in the book but it's confusing me, I'll attach a picture.

2m7zp88.jpg


So I get lost where it starts talking about a cross-sectional area all of a sudden multiplying by ∏. What's going on here?!
 
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  • #2
What's the area of a circle of radius r? What if the radius is y instead of r?
 
  • #3
Feodalherren said:

Homework Statement



Show that the volume of a sphere of radius r is

V = (4/3)πr^2
Probably a typo - the volume is (4/3)##\pi r^3##.

Feodalherren said:

Homework Equations



calculus, integration

The Attempt at a Solution



I have the solution in the book but it's confusing me, I'll attach a picture.

2m7zp88.jpg


So I get lost where it starts talking about a cross-sectional area all of a sudden multiplying by ∏. What's going on here?!
The book is using disks that are oriented vertically (the x-axis intersects each disk perpendicularly). The volume of such a disk is its area times its thickness, dx.
 

What is the formula for finding the volume of a sphere using calculus and integration?

The formula for finding the volume of a sphere using calculus and integration is V = ∫πr^2dx, where r is the radius of the sphere and dx is the small element of volume.

What is the process for solving for the volume of a sphere using calculus and integration?

The process for solving for the volume of a sphere using calculus and integration involves setting up the integral using the formula V = ∫πr^2dx, determining the limits of integration, and then evaluating the integral using integration techniques such as substitution or u-substitution.

What are the limits of integration for finding the volume of a sphere using calculus and integration?

The limits of integration for finding the volume of a sphere using calculus and integration are -r to r, as this represents the range of the radius of the sphere.

Can the volume of a sphere be found using other methods besides calculus and integration?

Yes, the volume of a sphere can also be found using the formula V = (4/3)πr^3 which is derived from geometry and does not require calculus or integration.

How accurate is the volume of a sphere found using calculus and integration compared to other methods?

The volume of a sphere found using calculus and integration is more accurate as it takes into account the infinitesimal elements of the sphere, while the formula V = (4/3)πr^3 is an approximation and may have a larger margin of error.

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