Yahoo Answers: Answers and Comments for If R = 2.400 ± 0.003, what is the relative uncertainty for R−2? Plz also provide explanation/solution.? [Physics]
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From Anonymous
enCA
Sun, 08 Sep 2019 19:51:37 +0000
3
Yahoo Answers: Answers and Comments for If R = 2.400 ± 0.003, what is the relative uncertainty for R−2? Plz also provide explanation/solution.? [Physics]
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From Andrew Smith: There is a rule of thumb method and there is f...
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Sun, 08 Sep 2019 23:37:30 +0000
There is a rule of thumb method and there is formal analysis.
The rule of thumb for small errors and for multiplication and division means that you ADD THE FRACTIONAL ERROR for each multiplication.
Which means that for raising to a power you multiply the fractional error by the absolute value of the power to get the fractional error in the result.
ie the fractional error would be approximately ( 0.003/2.4)*(2) = 2 * 0.003/2.4 = 0.0025
Formally you calculate the lowest result and the largest possible result.
This gives the absolute error which you could THEN turn into a fraction.
ie ( 2.4 + 0.003)^(2) < R^(2) < (2.4  0.003)^(2)
0.173178 < R ^(2) < 0.174406
The EXPECTATION VALUE is 2.4 ^ (2)= 0.173611
Now put the differences as a fraction of the expectation.
(0.1736111 0.1731779) / 0.1736111 = 0.0025 ( just as we got for the first method )
The second method is more complex but it is the only TRUE method for finding errors.
The rule of thumb works fine if the errors are small compared to the target and if the formula is a simple one that contains only one basic process.

From NCS: If you raise a value to the nth power, you mul...
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Sun, 08 Sep 2019 23:07:55 +0000
If you raise a value to the nth power, you multiply the uncertainty by n.
For this problem, n = 2
and so the relative uncertainty is ±0.006

From billrussell42: the same, ± 0.003
subtraction or addition, th...
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Sun, 08 Sep 2019 19:56:35 +0000
the same, ± 0.003
subtraction or addition, the error is by decimal place. Assuming 2 is an exact number, then the error does not change.
of course if 2 is only accurate to 2±1, then the uncertainty is ±1
edit, re correction.
best method is to calculate 1/2.403² and 1/2.397²

From Anonymous: First tell me what the relative uncertainty is...
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Sun, 08 Sep 2019 20:52:12 +0000
First tell me what the relative uncertainty is for me getting with your mother