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Uncertainty of the function? My answer is a bit different

Thread starter giantf
Start date May 15, 2017
Tags

Bit Error propagation Function Uncertainties Uncertainty Uncertainty propagation Uncertainty relation

1 reply · 2K views · last reply May 16, 2017

giantf

Thread starter
May 15, 2017

#1

Homework Statement

Printed problem: A function f is given by f = 3(x + y)/z, where x = (9.57 ± 0.05), y = (6.22 ± 0.04) and z = (8.64 ± 0.02). Calculate the absolute uncertainty in f. Round your answer to three significant figures.

Homework Equations

The Attempt at a Solution

Handwritten working for uncertainty of f = 3(x+y)/z with x = 9.57 ± 0.05, y = 6.22 ± 0.04, z = 8.64 ± 0.02. Best value 3(9.57+6.22)/8.64 = 5.48264, then 5.48264(0.05+0.04+0.02/8.64) giving 0.506.

The answer is different though,

Screenshot of a Correct Answers box listing four values: 0.0257 (with precision: 3), 0.0256 (with precision: 3), 0.044 (with precision: 3), and 0.0439 (with precision: 3).

Discussion

haruspex

Science Advisor

Homework Helper

Insights Author

Gold Member

May 16, 2017

#2

giantf said:

Homework Statement

View attachment 203587

Homework Equations
The Attempt at a Solution

View attachment 203588
The answer is different though,
View attachment 203589

Does it not strike you as odd that you divided δz by z but did not divide δx+δy by anything?
Check your formula.

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