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ERIC Number: EJ1168676
Record Type: Journal
Publication Date: 2018-Feb
Pages: 5
Abstractor: As Provided
ISSN: ISSN-0031-921X
The Indeterminate Case of Classical Static Friction When Coupled with Tension
Hahn, Kenneth D.; Russell, Jacob M.
Physics Teacher, v56 n2 p83-87 Feb 2018
It has been noted that the static friction force poses challenges for students and, at times, even their instructors. Unlike the gravitational force, which has a precise and unambiguous magnitude (F[subscript G] = mg), the magnitude and direction of the static friction force depend on other forces at play. Friction can be understood rather well in terms of complicated atomic-scale interactions between surfaces. Ringlein and Robbins survey aspects of the atomic origins of friction, and Folkerts explores factors that affect the value of static friction. However, what students typically encounter in an introductory course ignores the atomic origins of friction (beyond perhaps a brief overview of the atomic model). The rules of dry friction (i.e., non-lubricated surfaces in contact) taught in introductory physics were originally published in 1699 by Guillaume Amontons. Amontons's first law states that the force of friction is directly proportional to the applied load, i.e., f = [subscript µ]F[subscript N], where F[subscript N] is the normal force and µ is the coefficient of friction. His second law states that the force of friction is independent of the "macroscopic" area of contact. These laws were verified by Coulomb in 1781.
American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A