When finding uncertainties in measurements, I know that if you are adding or subtracting, you must add the uncertainties of the two values. But what do I do if I multiply/divide?

Answer 1

If X=A*B or X=A/B, then the uncertainty in X is:

X*sqrt( ((uncertainty in A)/A)^2 + ((uncertainty in B/B))^2 )

Answer 2

I'm not entirely sure what you mean, but after a thorough search through notes I think I might get it... correct me if I'm wrong?

I need to use relative uncertainties, and then use the relative uncertainty to find the uncertainty?

(I know how to do both of those, I just want to make sure that that is what I'm supposed to be doing.)

Thanks

Answer 3

Yes, since the uncertainty of a product or quotient of two values depends on the uncertainty of each of those two values. (The more uncertain the values, the more uncertain the product or quotient of those values.)