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Re: POSITIVE work in cyclic motion

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  • Re: POSITIVE work in cyclic motion

    Net worked performed by a "machine" is not a function of the
    beginning and final positions (be that of water, people, apples, or
    pistons). I think you should get your hands on a good thermodynamics
    text and read-up on "efficiency". It was to describe systems such as
    this that the concept of efficiency was developed to accound for the lost
    work performed. Just because a system ends up in the same configuration
    that it began, does not mean the net work done by the system was zero.
    What you say with the swimmer is analogous to me walking across town and
    back again. Are you saying I performed no work in doing so simply
    because I ended up where I began? Does a fan in a closed room do no
    work? I would sure like to know where all that electricity is going if
    it's not going towards work -- maybe I should call the electric company
    and ask for a refund --- will you back me up on this?
    Yes Craig, there is work done, unfortunately, due to friction
    etc, the air goes back to its original state of inertia and the fan must
    continue to turn to keep the air flowing, as the swimmer must keep
    "stroking?" to keep the water moving about him/her. The swimmer does
    some work, but then the friction between water molecules and
    quasi-equilibrium effects cause the water to loose kinematic energy, so
    he/she has to continually add work.

    John Smith