Annulus

Pronunciation: /ˈæn yə ləs/ ?

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)
Manipulative 1: Annulus. Created with GeoGebra.

An annulus is the region between two concentric circles.[1] The area of the annulus is the difference between the areas of the circles: A = π(r12 - r22) where r1 > r2.

check mark Understanding Check

What is the area of an annulus with an inner radius of 1m and an outer radius of 3m?

Click here for the answer.

Examples of Annulus

A roll of paper towels is an annulus.
Figure 2: Roll of paper towels
A roll of pipe tape is an annulus.
Figure 3: Roll of pipe tape
A pipe is an annulus.
Figure 4: Pipe

Challenge

1. A pipe has an inner radius of 3 cm. It has an outer radius of 3.5 cm. It is 100 cm long. What is the total volume of the pipe, not including the empty space inside?

Click here for a hint.

Click here for the answer.

2. The same pipe is made of a metal alloy with a density of 3g/cm3. What is the mass of the pipe in challenge 1?

Click here for the answer.

References

  1. annulus. http://wordnet.princeton.edu/. WordNet. Princeton University. (Accessed: 2011-01-08). http://wordnetweb.princeton.edu/perl/webwn?s=annulus&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h=.
  2. Stöcker, K.H.. The Elements of Constructive Geometry, Inductively Presented, pp 44-45. Translated by Noetling, William A.M, C.E.. Silver, Burdett & Company, 1897. (Accessed: 2009-12-28). http://www.archive.org/stream/elementsofconstr00noetrich#page/44/mode/1up/search/annulus.

Cite this article as:


Annulus. 2009-12-26. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/a/annulus.html.

Translations

Image Credits

  • All images and manipulatives are by David McAdams unless otherwise stated. All images by David McAdams are Copyright © Life is a Story Problem LLC and are licensed under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
  • Figure 2: Roll of paper towels: UNKNOWN. UNKNOWN.
  • Figure 3: Roll of pipe tape: UNKNOWN. UNKNOWN.
  • Figure 4: Pipe: UNKNOWN. UNKNOWN.

Revision History


2009-12-27: Added "Reference" and "More Information" (McAdams, David.)
2008-12-19: Changed figure 1 to a manipulative (McAdams, David.)
2008-06-23: Reorganized content, added challenge and understanding check (McAdams, David.)
2008-04-18: Added illustrations (McAdams, David.)
2008-04-17: Initial version (McAdams, David.)

All Math Words Encyclopedia is a service of Life is a Story Problem LLC.
Copyright © 2005-2011 Life is a Story Problem LLC. All rights reserved.
Creative Commons License This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License