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Home Conservation Laws Work: The Transfer of Mechanical Energy Summary  
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Summary  WorkWork is a measure of the transfer of mechanical energy, i.e., the transfer of energy by a force rather than by heat conduction. When the force is constant, work can usually be calculated as W = F_{II}d , [only if the force is constant] where d is simply a less cumbersome notation for Δr, the vector from the initial position to the final position. Thus,
When the force is not constant, the above equation should be generalized as the area under the graph of F_{II} versus d. Machines such as pulleys, levers, and gears may increase or decrease a force, but they can never increase or decrease the amount of work done. That would violate conservation of energy unless the machine had some source of stored energy or some way to accept and store up energy. There are some situations in which the equation W = Fk d is ambiguous or not true, and these issues are discussed rigorously in section 3.6. However, problems can usually be avoided by analyzing the types of energy being transferred before plunging into the math. In any case there is no substitute for a physical understanding of the processes involved. The techniques developed for calculating work can also be applied to the calculation of potential energy. We fix some position as a reference position, and calculate the potential energy for some other position, x, as PE_{x} = W_{ref→x }. The following two equations for potential energy have broader significance than might be suspected based on the limited situations in which they were derived:


Home Conservation Laws Work: The Transfer of Mechanical Energy Summary 