Sig Figs query for a steady flow pipe

AI Thread Summary
The discussion centers on the correct application of significant figures (sig figs) in a lab report for calculating pressure differences (Δp) in an experiment measuring the Reynolds number. The user is confused about how to represent their results, particularly when rounding values derived from measurements, such as Zw in mm. It is clarified that while rounding to two significant figures is acceptable for final results, calculations should be performed using full precision or guard digits to avoid inaccuracies. The importance of distinguishing between reported values and those used in calculations is emphasized to ensure proper treatment of uncertainties. Accurate representation of data is crucial for the integrity of scientific reporting.
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Homework Statement



First let me say I'm new to lab reports at Uni, and I'm dreadful at them...

I'm having issues with how many sig figs to correctly display on a data table for an experiment I've done to investigate the Reynolds number. One particular step is to find Δp at different stages on a manometer using the equation Δp=(ρwater-ρatm)gΔ(Zw) with Zw being the difference between the left and right hand side of the manometer. all my Zw values are in mm; for example one of them is 33mm, using the equation for that particular value I get 323 Pa, I've looked around and it seems that the value I should display on the table is 320 Pa as the value I obtained should have the same SF as the lowest SF of the value used to calculate it. This seems ok for lower values but looks wrong at higher values because it feels like I'm rounding up and down a lot of the value. I would be thankful if someone could tell me if I'm going wrong and the correct procedure when dealing with SFs from measurements taken in experiments.

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What do you mean with higher values?
Rounding to two significant figures is fine for a final result. It is not a proper treatment of uncertainties anyway...
 
Don't mistake reported values for those used in calculations. Your report should contain rounded numbers, but you should never used these rounded values in your calculations. Use either full precision as spit out by your calculator, or at least use so called guard digits - that is, use several digits more than you are reporting.
 
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