ProjectFrostbite Posted September 29, 2013 Report Share Posted September 29, 2013 How do I work out the uncertainies in my IA?I know about how to get them initially, but how do I handle them taking my IA to its conclusion?Can I simply add the uncertainties if I am multiplying two numbers for a third, or do I need to add the percentage errors and then work out the actual error from this?How many significant figures should I take my results to?Help Reply Link to post Share on other sites More sharing options...
Guest B.E.P. Posted September 30, 2013 Report Share Posted September 30, 2013 Look:If you are adding/subtracting two numbers, then you must add the absolute uncertainties:(2.0 +- 0.3) + (0.3 +- 0.4) = 2.3 +- 0.7(2.0 +- 0.3) - (0.3 +- 0.4) = 1.7 +- 0.7If you are multiplying/diving two numbers, then you must add the percent uncertainties:(2.0 +- 0.1) x (3.0 +- 0.3) = 6.0 (I will keep this as it is until I find out the absolute uncertaintyPercent uncertainties:0.1/2.0 = 0.05x100 = 5%0.3/3.0 = 0.10x100 = 10%5% + 10% = 15%Converting it back to absolute uncertainties:15/100=0.15 x 6.0 = 0.9Therefore, the answer is 6.0 +- 0.9Concerning significant figures, these are the rules I follow:Make sure your absolute uncertainty is to one significant figure.Make sure your uncertainties and your values are to the same decimal point.For example, if this question:(2.0 +- 0.2) x (3.0 +- 0.3) = 6.0 (I will keep this as it is until I find out the absolute uncertainty)Percent uncertainties:0.2/2.0 = 0.10x100 = 10%0.3/3.0 = 0.10x100 = 10%10% + 10% = 20%Converting it back to absolute uncertainties:20/100=0.20 x 6.0 = 1.2Since uncertainties must be to one significant figure, then the uncertainty will be reported as 1Therefore, the answer is 6 +- 1I hope this is clear enough! Reply Link to post Share on other sites More sharing options...
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