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Old 12-09-2007, 03:52 PM   #6
gjoc
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Join Date: May 2007
Location: Arlington, VA
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Quote:
Originally Posted by lethalfang View Post
2) The tension bar itself weights a few ounces, does that introduce an error?

In fact, it does, but the mass of the tension bar << mass of the dropweight, thus the effect is negligible.
Well done, although I have to disagree with your last point.

There is no “error” introduced into any of this by the bar.

The total clockwise (in your drawing) torque applied to the drum is equal to the sum of two torques, the weight of the bar times the horizontal distance of the C/G of the bar from the center of the drum, plus the weight of the weight times the horizontal distance of the C/G of the weight from the center of the drum.

The two torques go up and down together by the same percentage, with any change in angle of the bar, since both C/Gs move back and forth horizontally together by the same percentage, so there’s no error being introduced.
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