Compare volume formula to integration

In summary: The integral from 0 to 2\pi gives you the area of the circle with radius 1 centered at the origin and angle \theta.
  • #1
JProgrammer
20
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So I need to compare the results of the volume formula of a cylinder to the results of the integration.

In geometry, you learn that the volume of a cylinder is given by V = πr2h, where r is the radius and h is the height of the cylinder. Use integration in cylindrical coordinates to confirm the formula V. To do so, let r = 1 and h = 2, and fill in the limits in the integration below. Integrate, then compare the results (one from V and one from integration).

∭1▒〖𝑟 𝑑𝑧 𝑑𝑟 𝑑𝜃〗

The result from the formula is: 2pi

The question I have is what would the cylindrical coordinates be and how would I use them for integration?
 
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  • #2
JProgrammer said:
The question I have is what would the cylindrical coordinates be
Why don't you look in Wikipedia, MathWorld or the Encyclopedia of Mathematics? See especially the volume element. In fact, you should first make an effort to get a hold of your course materials (a textbook, lecture notes or handouts) because studying them is much more efficient. You should consult online forums for definitions only if it is impossible to obtain them from your instructor or other students.

JProgrammer said:
and how would I use them for integration?
The same as for Cartesian coordinates. You break the volume into small volume elements. Each element is obtained by fixing a point $(\theta,r,z)$ and then varying each coordinate slightly. The resulting volume element is not exactly a cuboid, but can be appriximately considered as such if the coordinate variations are small.
 
  • #3
JProgrammer said:
So I need to compare the results of the volume formula of a cylinder to the results of the integration.

In geometry, you learn that the volume of a cylinder is given by V = πr2h, where r is the radius and h is the height of the cylinder. Use integration in cylindrical coordinates to confirm the formula V. To do so, let r = 1 and h = 2, and fill in the limits in the integration below. Integrate, then compare the results (one from V and one from integration).

∭1▒〖𝑟 𝑑𝑧 𝑑𝑟 𝑑𝜃〗

The result from the formula is: 2pi

The question I have is what would the cylindrical coordinates be and how would I use them for integration?

The point is, as the problem said, to 'fill in the limits in the integration below'. "r" is the distance from the central axis to a point in the cylinder. To cover the entire cylinder r will go from the axis. 0, to the cylinder . You are told that the cylinder has radius 1 so your integration, with respect to r, will go from r= 0, at the center, to 1. "z" is measured along the length of the cylinder. You are told that this is h= 2 so to cover the entire cylinder the integration with respect to z is from 0 to h. Finally, [tex]\theta[/tex] is the angle measured around the cylinder. To cover the entire cylinder [tex]\theta[/tex] must go from 0 to [tex]2\pi[/tex]. The integral you need to do is
[tex]\int_{\theta= 0}^{2\pi}\int_{r= 0}^1\int_{z= 0}^2 r dzdrd\theta[/tex].

What does that integral give you?
 

FAQ: Compare volume formula to integration

What is the volume formula for a solid?

The volume formula for a solid is the product of its length, width, and height. This is represented as V = lwh.

How is integration related to volume?

Integration is a mathematical process that can be used to find the volume of irregularly shaped objects by breaking them down into infinitesimally small pieces and summing their volumes.

Can integration be used to find the volume of any object?

Yes, integration can be used to find the volume of any object as long as its shape can be described using a mathematical function.

Are there any other methods for finding volume besides integration?

Yes, there are other methods such as using the volume formula for regular shapes like cubes and spheres, or using the displacement method for irregularly shaped objects.

What are some real-life applications of comparing volume formula to integration?

This comparison is commonly used in engineering and architecture to calculate the volume of complex structures. It is also used in physics to determine the volume of objects with varying densities, such as in fluid mechanics.

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