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Revision as of 15:27, 30 November 2002 by Maury Markowitz (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Working mass is a mass against which a system operates in order to produce acceleration. All acceleration requires an exchange of momentum, which can be thought of as the "unit of movement". For one body to speed up, another must slow down. Momentum is contained in mass, as given by the formula P = mv, where P is the momentum, m the mass, and v the velocity. The velocity of a body is easily changable, but in most cases the mass is not, which makes it important.
The term working mass is used primarily in the aeronautics field. In more "down to earth" examples the working mass is typically provided by the Earth or water, which contains so much momentum in comparison to most vehicles that the amount it gains or loses can be ignored. However in the case of an aircraft the working mass is the air, and in the case of a rocket, the rocket fuel itself. In both cases the exchange of momentum is quite dramatic, blowing people over on the ground to accelerate a plane for instance.