Moments to remember—The conditions for equating torque and rate of change of angular momentum
作者:
Fredy R. Zypman,
期刊:
American Journal of Physics
(AIP Available online 1990)
卷期:
Volume 58,
issue 1
页码: 41-43
ISSN:0002-9505
年代: 1990
DOI:10.1119/1.16316
出版商: American Association of Physics Teachers
关键词: ANGULAR MOMENTUM;TORQUE;RIGID BODIES;CLASSICAL MECHANICS;VECTORS
数据来源: AIP
摘要:
It is a well‐known but frequently forgotten fact that the net external torque on a system of particles is equal to the rate of change of angular momentum only if the point about which moments are taken satisfies certain stringent conditions: The point must have zero acceleration, or it must be the center of mass, or its instantaneous acceleration must be directly toward or away from the center of mass. A simple problem in rigid‐body mechanics has been solved by Crawford, taking moments about the center of mass. It is shown here that the problem may also be solved using a point that doesnotsatisfy any of these conditions, in which case a more general equation is required. An external fixed point may also be used for calculating moments. When carefully executed, all correct approaches yield the same solution.
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