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ERIC Number: EJ892020
Record Type: Journal
Publication Date: 2007-Sep
Pages: 2
Abstractor: As Provided
Reference Count: 0
ISSN: ISSN-0031-921X
Pulling a Door Open by Pushing on It
van den Berg, Willem H.
Physics Teacher, v45 n6 p361-362 Sep 2007
Ordinarily, opening a door by pulling on the knob or handle causes a net torque on the door, and hence an angular acceleration, about a "vertical" axis. However, it may be that the top or bottom of the door sticks to the door frame; this horizontal force perpendicular to the plane of the door causes a torque on the door about a "horizontal" axis. This latter torque is countered by an opposite torque caused by horizontal forces exerted by the hinges; the result is that the door is deformed but does not readily open. The horizontal forces between the door and the hinges can potentially tear loose the hinges. When the sticking is released, the elastic potential energy stored in the deformation of the door becomes the alternating kinetic and potential energy of an annoying oscillation.
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