Document Type
Article
Publication Date
2026
DOI
10.1119/5.0270215
Publication Title
The Physics Teacher
Volume
64
Issue
6
Pages
557 (1 pp.)
Abstract
The article focuses on the sphericity index χ, a measure of how much an object's shape deviates from a perfect sphere (χ = 1), defined approximately as χ ≈ 4.836V²ᐟ³/A for an object with volume V and surface area A. It presents a problem to derive the sphericity index expression for a right circular cylinder with height h = ar and radius r, where a > 0, and to analyze the behavior of χ as a function of a, including identifying the value of a that maximizes χ. The article also encourages readers to estimate their own cylindrical sphericity index and directs them to an online resource for solutions. This content is part of a series of brief estimation problems known as Fermi Questions.
Rights
© 2026 The Author.
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in:
Adam, J. (2026). Sir lyndrical John revisited: The sphericity index [Question/ Answer]. Physics Teacher, 64(6), 557
and may be found at: https://doi.org/10.1119/5.0270215
Original Publication Citation
Adam, J. (2026). Sir lyndrical John revisited: The sphericity index. The Physics Teacher, 64(6), 557. https://doi.org/10.1119/5.0270215
ORCID
0000-0001-5537-2889 (Adam)
Repository Citation
Adam, John, "Sir Lyndrical John Revisited: The Sphericity Index" (2026). Mathematics & Statistics Faculty Publications. 347.
https://digitalcommons.odu.edu/mathstat_fac_pubs/347