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ERIC Number: EJ1004672
Record Type: Journal
Publication Date: 2013-Feb
Pages: 3
Abstractor: As Provided
Reference Count: 6
ISSN: ISSN-0031-921X
The Effect of Friction in Pulleys on the Tension in Cables and Strings
Martell, Eric C.; Martell, Verda Beth
Physics Teacher, v51 n2 p98-100 Feb 2013
Atwood's machine is used in countless introductory physics classes as an illustration of Newton's second law. Initially, the analysis is performed assuming the pulley and string are massless and the axle is frictionless. Although the mass of the pulley is often included when the problem is revisited later in the context of rotational dynamics, the mass of the string and the friction associated with the axle are less frequently discussed. Two questions then arise: 1) If we are ignoring these effects, how realistic is our model? and 2) How can we determine when or if we need to incorporate these effects in order to make our model match up with reality? These questions are connected to fundamental issues faced by physics teachers, namely the frustration students sometimes feel when they do not see how they can use the results of the problems they have been working on and how we can help our students develop effective models for physical systems. (Contains 1 table and 2 figures.)
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