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Re: [Phys-l] Energy Question Negative Reps.



At 01:58 PM 1/12/2007, you wrote:
If no net change in KE occurs from beginning to end, and no net change in PE
occurs from beginning to end, then the lifter did no work on the barbell -
pure and simple. Why is there a discussion on this? Are we making up an
alternate definition of work?

The fact that this doesn't jibe with our intuition probably just means that
the work-KE theorem is probably not the clearest way to present physics to
students.

Bob at PC


I prefer to suppose that people who treat a servo motor like a lossless
jack will draw the conclusion indicated in Bob's initial question.

And people who treat a screw jack like a lossless jack
(as did Feynman,) make only a factor of two error.



Brian Whatcott Altus OK Eureka!