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Phy 121

Your 'question form' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

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Energy Conversion Lab

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I've come to this step in the lab:

In the space below, report in five comma-delimited lines, one for each set of trials, the length of the rubber band, the number of dominoes supported at this length, the mean and the standard deviation of the sliding distance in cm, and the energy associated with the stretch.

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I have calculated the energy associated with the stretch by taking the distance of the stretch and multiplying it by the force in Newtons I had calibrated for that stretch. For example if .38 Newtons is associated with a band length of 8.0cm. I would multiply .38N by 8.0 cm to get 3.04Newton cm. BUT, that doesn't seem right to me. I think I would need to calculate the amount of stretch from an unstreched rubber band. In this case it would be the stretch of .2cm times .38N which would equal .076 Newton cm. ???Is my second assumption the correct one, that I get my distance from the delta in band length???

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You second assumption is more nearly correct.

Work is the product of the force and the displacement through which the force is applied.

The rubber band exerts no force when the length is less than a certain length, which from your information I assume to be 7.8 cm.

However .38 Newtons is the maximum force exerted over that .2 cm displacement, not the average force.

Presumably the force at the beginning of that .2 cm interval is zero, and if so your average force for the interval would be only .19 N.

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