Extending the application of the relativity principle: Some pedogogical advantages

Although textbooks usually present the conservation laws of energy and momentum only in the laboratory frame of reference, it is important that an introductory physics course show that they are valid in any inertial frame. It can be useful to apply the conservation laws in more than one frame of reference so as to highlight that they are precise only in closed systems. This is of particular note if one of the interacting partners is of near-infinite mass, whose share of the redistributed energy cannot always be neglected. In this sense, the nation of ''infinitely large mass'' is frame dependent. Balancing the energy and momentum in more than one frame of reference can help resolve some common difficulties with regard to energy conservation. We show also that the energy-work theorem holds in noninertial frames where inertial forces are treated as external. (C) 1997 American Association of Physics Teachers.