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# How to calculate the error in V & U? watch

1. The error of the ruler that measured the length of V and U had an error of 0.05cm, however what happens when we want the errors of 1/U and 1/V?
2. (Original post by Mulkeen)
The error of the ruler that measured the length of V and U had an error of 0.05cm, however what happens when we want the errors of 1/U and 1/V?
Hello,

As 1/U (or 1/V) is equivalent to U-1 (or V-1), I would imagine that you would multiply the proportional uncertainty by -1. As uncertainties can be added or subtracted, this is just equivalent to the original proportional uncertainty.

e.g. If U = 2cm, the proportional uncertainty is 2.5%. The gives 1/U the final value of 0.5cm-1 with an uncertainty of 2.5% (or 0.0125cm-1 either way). I hope that this has been helpful.
3. (Original post by Mulkeen)
The error of the ruler that measured the length of V and U had an error of 0.05cm, however what happens when we want the errors of 1/U and 1/V?
In the case of powers the relative uncertainty is multiplied by the power (its absolute value is taken).
4. (Original post by Phichi)
In the case of powers the relative uncertainty is multiplied by the power (its absolute value is taken).
So could give me an example if U=5cm +/- 0.05cm please? What would the error in 1/U be?

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