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Old 5th Feb 2012, 09:46
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cwatters
 
Join Date: Dec 2001
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Work = force * displacement

If displacement = zero then
work = zero.

In the case of a jet it doesn't mean no fuel is consumed. Just that the engines are 0% efficient (if you define efficiency in the right terms). All the fuel burnt is wasted accelerating air, heating it up, making noise etc.

The equation also explains how fridge magnets manage to stay up without an energy source. They don't need one as they also do no work.
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