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Homework Help: What does "Work done on the object" mean

  1. Nov 12, 2005 #1
    what is the difference between "work done on the object" and "work done by the net force"? if there is a difference, can u give me an example? thx thx
  2. jcsd
  3. Nov 12, 2005 #2


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    Homework Helper

    "Work done on the object" is a general phrase ;
    the source Force can be specified (as, "W on object by friction Force"),
    they can be a subset of Forces ("total W by all the conservative Forces") (=PE's),
    they can be the entire set of all Forces applied to the object.
    The object can be a system composed of multiple parts, with the parts
    able to Exchange Energy with another part.
    The approach introduced by this phrase can be extended to treat thermal Energy transfer.

    Here, the source Force might *by implication* be a Force that has been
    the focus of the last paragraph or two.

    "Work done by the net Force" is a lousy phrase ;
    it rewards students who do not distinguish cause (Forces, with sources)
    from effect (ma).
    It avoids mention of the most important item of the process (the OBJECT which Force is applied to...). It is always equal to the change in the (implied) object's KE, so it is at best a riddle-name for d KE.
    Last edited: Nov 12, 2005
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