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Experimental accuracy calculations
How do you calculate these.
If you have two figures, 4.13 +/-0.005 and 9.36 +/- 0.005 and multiply them together, what is the inaccuracy of the new reading?
How about you measure a cube's side to be 6.15 +/- 0.025 (from a ruler), what would be the accuracy of the cube's volume?
Thanks for any help.
If you have two figures, 4.13 +/-0.005 and 9.36 +/- 0.005 and multiply them together, what is the inaccuracy of the new reading?
How about you measure a cube's side to be 6.15 +/- 0.025 (from a ruler), what would be the accuracy of the cube's volume?
Thanks for any help.
Also, where you have inaccuracy from the measuring tools, you might also get it from human error. Can someone remind me how to find the accuracy when you take 5 readings, say:
5.23, 5.24, 5.20, 5.24, 5.22
Would it be the range divided by the average?
(5.24-5.20)/[(5.23 + 5.24 + 5.20 + 5.24 + 5.22)/5] which is 0.765%
Would this then override the accuracy of the equipment, say meade a measurement like 5.32 +/- 0.005? Or would you add it? It seems wrong to add it but I just want to check.
Also is it correct to only do this for results which have relied on humans recording things (eg. stopwatch compared to scales where there is no possibility for human error).
Thanks again, rep definatly awarded.
5.23, 5.24, 5.20, 5.24, 5.22
Would it be the range divided by the average?
(5.24-5.20)/[(5.23 + 5.24 + 5.20 + 5.24 + 5.22)/5] which is 0.765%
Would this then override the accuracy of the equipment, say meade a measurement like 5.32 +/- 0.005? Or would you add it? It seems wrong to add it but I just want to check.
Also is it correct to only do this for results which have relied on humans recording things (eg. stopwatch compared to scales where there is no possibility for human error).
Thanks again, rep definatly awarded.
When you multiply values you add the PERCENTAGE uncertainty. If you look in the "ultimate thread" there are v good examples at the beginning. We didn't have them today for group 1 though. Not sure how similar the exams ar, but if it is the same then you do not need to worry about % uncertainties.
blunty
when you are multiplying values i think you add the uncertainties.
That's what I thought too, but I tried it and it doesn't work. eg.
7.1 (+/- 0.05) squared = 50.41 (+/- 0.1) ?
lower bound = 7.1 - 0.05 = 7.05, squared = 49.7025
upper bound = 7.1 + 0.05 = 7.15, squared = 51.1225
This is different from what adding suggests, which is 49.41 - 51.41
Zany
When you multiply values you add the PERCENTAGE uncertainty. If you look in the "ultimate thread" there are v good examples at the beginning. We didn't have them today for group 1 though. Not sure how similar the exams ar, but if it is the same then you do not need to worry about % uncertainties.
Okay thankyou very much. So you should convert to percentage as soon as possible and before you do calculations with them always?
I will have a look right now. CHeers.
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